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*
Departments of Biology,
Plant Pathology, Physiology and Weed Science, and
Biomedical Sciences and Pathobiology, Virginia-Maryland Regional College of Veterinary Medicine, Virginia Tech, Blacksburg, VA 24061; and
Amgen Institute, Ontario Cancer Institute, Toronto, Ontario, Canada
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Abstract |
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 Top Abstract IntroductionMaterials and MethodsResultsDiscussionReferences |
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Introduction |
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TopAbstractIntroductionMaterials and MethodsResultsDiscussionReferences |
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CD44 is a family of cell surface glycoproteins with proposed functions in extracellular matrix (ECM) binding, cell migration, lymphopoiesis, and lymphocyte homing (9). CD44 molecules are produced by alternate splicing of multiple exons of a single gene and by different posttranslational modifications in different cell types (9). The principal ligand of CD44 has been identified as hyaluronic acid (HA), a major component of the ECM.
We and others have shown that activated CTL, NK/lymphokine-activated killer (LAK) (4) cells, and cytotoxic double-negative T cells, express increased levels of CD44 and mediate efficient lysis of target cells when activated through CD44 (10, 11). Inasmuch as CD44 also plays a major role in the lymphocyte adhesion to the endothelial cells, we have hypothesized that dysregulation in the interaction between cytolytic lymphocytes expressing CD44 and endothelial cells bearing the appropriate ligand could lead to endothelial cell injury and VLS (10, 12). To this end, we have shown that IL-2-induced VLS is markedly decreased in mice deficient in perforin and Fas ligand, thereby suggesting the involvement of cytotoxic lymphocytes in VLS (12). Also, treatment with IL-2 caused a significant increase in the expression of CD44, migration and perivascular infiltration of lymphocytes in various organs, and endothelial cell damage (12).
In the current study we further tested the hypothesis that CD44 is directly involved in the injury to the endothelial cells caused by CTL and LAK cells during IL-2-induced VLS. To this effect we used CD44 knockout (KO) mice and observed that such mice exhibit markedly diminished VLS following IL-2-treatment. Our data also suggest that blocking CD44 helps in reducing the IL-2-induced VLS; therefore, such an approach may serve as a useful tool to prevent the endothelial cell damage seen in a variety of clinical disorders.
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Materials and Methods |
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TopAbstractIntroductionMaterials and MethodsResultsDiscussionReferences |
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Adult female C57BL/6 mice (CD44+, wild type) were purchased from the National Institutes of Health (Bethesda, MD). CD44 KO mice with C57BL/6 background were generated at Amgen Institute (Toronto, Canada), bred in the animal facilities at Virginia Tech, and screened for the CD44 deletion. The phenotype of these mice has been described previously (13).
Cell lines
P815, a mastocytoma resistant to NK cells, was maintained in vitro by serial passages in tissue culture medium, RPMI 1640 containing 10% FCS, as previously described (12).
Abs and reagents
Monoclonal MEL-14 (lymphocyte homing receptor; rat IgG) and anti-LFA-1 (M17/4; rat IgG) Abs were grown in vitro as previously described (12). The FITC-anti-CD3, PE-anti-CD44, PE-anti-CD8, and FITC-anti-CD4 mAbs were purchased from PharMingen (San Diego, CA). FITC-conjugated F(ab')2 of goat anti-Syrian hamster IgG was purchased from Jackson ImmunoResearch Laboratories (West Grove, PA). F(ab')2 of anti-CD44 (IM7) mAbs were prepared by treatment with pepsin and passing the fragments over a protein A column (Pierce, Rockford, IL) (10). Evan’s blue dye was obtained from Sigma (St. Louis, MO).
Interleukins
Recombinant IL-2 was provided by Hoffmann-La Roche (Nutley, NJ) and by Dr. C. Reynolds (National Institutes of Health, Bethesda, MD).
Detection of surface molecules using immunofluorescence analysis
Splenic T cells and LN cells were analyzed for LFA-1 and other adhesion molecule expression using flow cytometry. For LFA-1 detection, the cells were incubated with anti-LFA-1 mAbs for 30 min on ice followed by washing three times. After washing, FITC-conjugated secondary Ab was added to detect the presence of LFA-1. The secondary Ab consisted of FITC-conjugated anti-rat IgG F(ab')2 (Cappel, Durham, NC). Negative controls consisted of fluorescence obtained by staining cells with FITC-conjugated secondary Ab alone. The expression of CD3, CD4, CD44, and CD8 was detected by staining the cells with PE- or FITC-conjugated Ab against these markers for 30 min on ice, followed by washing three times. Nonspecific staining was blocked by incubation of cells with 0.5% normal mouse serum for 30 min before staining with labeled Ab. Next, 10,000 cells were analyzed by flow cytometry (EPICS V, model 752, Miami, FL).
Quantitation of VLS
Vascular leak was studied by measuring the extravasation of Evans blue, which when given i.v. binds to plasma proteins, particularly albumin, and following extravasation can be detected in various organs as described previously (14). Vascular leak was induced by injecting IL-2 as previously described (12). Groups of five mice were injected i.p. with 65,000 U of rIL-2 or PBS as a control, three times a day for 3 days. On day 4 they received one injection in the morning and 2 h later were injected i.v. with 0.1 ml of 1% Evans blue in PBS. After 2 h the mice were bled to death under anesthesia, and the heart was perfused with heparin in PBS as described previously (15). The lungs and liver, where maximum extravasation is known to occur, were harvested and placed in formamide at 37°C overnight. The Evan’s blue in the organs was quantitated by measuring the absorbance of the supernatant at 650 nm with a spectrophotometer. The VLS seen in IL-2-treated mice was expressed as the percent increase in extravasation compared with that in PBS-treated controls and was calculated as: [(µg of dye in the organ of IL-2-treated mice) - (µg of dye in the organ of PBS-treated controls)]/(µg of dye in the organ of PBS-treated control) x 100. Each mouse was individually analyzed for vascular leak, and the data from five mice were pooled and expressed as the mean ± SEM percent increase in VLS in IL-2-treated mice compared with that in PBS-treated controls.
Use of anti-CD44 mAbs to block VLS
C57BL/6 wild-type mice were treated with IL-2 as described above along with 100 µg F(ab')2 of anti-CD44 (IM7) Abs/mouse/day for a period of 4 days. The control mice received IL-2 and 100 µg of normal rat IgG/mouse/day for a similar duration. In a similar experiment mice were also injected with IL-2 plus 500 µg of F(ab')2 of anti-CD44 mAbs or IL-2 plus 500 µg of normal rat IgG as a control. The VLS seen in these IL-2-treated mice was compared with the VLS seen in PBS-treated mice, and the data were expressed as the percent increase in extravasation as described above.
Histology
For histopathological studies, groups of five separate mice were injected with IL-2 or PBS as described earlier, and on day 4 lungs and liver were fixed in 10% formalin solution. The organs were embedded in paraffin, sectioned, and stained with hematoxylin and eosin. Perivascular infiltration was scaled by counting the number of lymphocytes infiltrating the vessel and averaging the minimum and maximum range for each group (12). Three samples were used for lung, and 10 samples were used for the liver.
Electron microscopy studies
Tissue samples were fixed in 5% glutaldehyde/4.4% formaldehyde/2.75% picric acid in 0.05 M sodium cacodylate buffer, pH 7.4. Samples were washed in a sodium cacodylate buffer. Samples were postfixed in osmium tetroxide, embedded in Polybed 812 resin (Polysciences, Warrington, PA), and studied with an electron microscope (12).
Adoptive transfer of cells into CD44 KO mice
Spleen cells (2x108 cells) from CD44+ (wild-type) or CD44-KO mice were injected i.p. into groups of four or five CD44-KO mice. These mice were injected with IL-2 as discussed above to induce VLS. After 4 days, the lungs and liver were harvested, and VLS was measured using the dye extravasation assay as described above. The IL-2-induced VLS was compared with that induced in PBS-treated CD44 KO mice, and the percent increase in extravasation was calculated as described above.
Proliferative responsiveness to HA
The proliferative responsiveness to HA was studied as described at length previously (16). Briefly, spleen cells from CD44+ (wild-type) or CD44 KO mice were cultured at a concentration of 6x105 cells/well in 96-well flat-bottom plates in 200 µl of medium. The cells were cultured in various concentrations of HA (Sigma) for 48 h at 37°C. The cultures were pulsed with [3H]thymidine 6 h before harvesting using a cell harvestor (Skatron, Sterling, VA), and the labeled DNA was counted in a liquid scintillation counter (16).
Mitogen stimulation
Spleen cells (1 x 106) from CD44+ (wild-type) or CD44 KO mice were cultured in the presence of Con A (5 µg/ml), anti-CD3 mAbs (1/100 final dilution of hybridoma supernatant), or LPS (100 µg/ml) for 48 h in 0.2 ml of medium in multiple wells of tissue culture plates as previously described (16). The cultures were pulsed with [3H]thymidine 6 h before harvesting using the cell harvester, and the labeled DNA was counted in a liquid scintillation counter as described above.
Generation of LAK cells
Nylon wool-nonadherant spleen cells from CD44 KO and CD44 wild-type mice were cultured for 48 h with 1000 U/ml of IL-2. The cells were harvested, and viable cells were purified on Ficoll-Hypaque (Sigma) density gradient centrifugation. The cells were next tested for cytotoxicity against P815 tumor targets. In some experiments anti-CD44 mAbs (5 µg/ml) were added at the initiation of LAK cell cultures with IL-2. Also, in other experiments anti-CD44 mAbs (5 µg/ml) were added while testing the cytotoxicity of LAK cells against P815 tumor targets. In the above experiments normal rat IgG (5 µg/ml) was used as a control for anti-CD44 mAbs.
Cytotoxicity
The ability of splenic T cells to lyse various tumor targets was tested using the 51Cr release assay (17, 18). Briefly, 5 x 106 target cells (P815) were labeled with 51NaCrO4 by incubating at 37°C for 1 h. Varying E:T cell ratios in triplicate were added in 96-well round-bottom plates (Falcon 3910, Becton Dickinson, Lincoln Park, NJ) and incubated for 4 h at 37°C. Spontaneous release was measured by incubating the 51Cr-labeled targets alone, and total release was determined by incubating the labeled target cells with 0.1 M SDS. The supernatants were harvested after 4 h, and radioactivity was measured with a gamma counter (TmAnalytic, Elk Grove Village, IL)
Statistical analysis
The VLS data in different strains of mice were compared using ANOVA, and p < 0.05 was considered to be statistically significant.
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Results |
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TopAbstractIntroductionMaterials and MethodsResultsDiscussionReferences |
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To phenotypically confirm the expression of CD44, the wild-type
and CD44 KO mice were screened using flow cytometry. To this end,
splenic T cells from wild-type or CD44 KO mice were stained with mAbs
against CD44 either immediately or following activation with Con
A. The data shown in Fig. 1
indicated
that T cells from CD44 KO mice failed to express CD44 even after
activation, while similar cells from wild-type mice expressed high
levels of CD44, which was further up-regulated following activation
with Con A.
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Previous studies from our laboratory demonstrated that splenic B
cells exhibit a strong proliferative response to stimulation with
hyaluronate, an important ligand for CD44 (12). We
therefore investigated whether the CD44 KO mice displayed a decreased
proliferative response to HA. To this end, spleen cells were cultured
in triplicate in the presence of HA for 48 h, and cell
proliferation was measured. As shown in Fig. 2, CD44 KO mice displayed a decrease in
response to stimulation with HA at all concentrations tested. It should
be noted that the T and B cells from CD44 KO mice responded normally to
stimulation with various mitogens. For example, when spleen cells from
CD44 KO mice were stimulated with LPS, they showed significant
proliferation (111,246 ± 4,657 cpm) comparable to that seen with
cells from CD44 wild-type mice (98,165 ± 872 cpm). Similarly, the
responses to anti-CD3 mAbs were comparable in CD44 KO and CD44
wild-type mice (159,145 ± 8,991 vs 159,347 ± 12,229 cpm,
respectively).
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To investigate the role of CD44 in IL-2-induced VLS, groups of five wild-type or CD44KO mice were injected with 65,000 U of IL-2 three times a day for 3 days and once on day 4. On the last day, the mice were injected with 1% Evans blue dye, and VLS was studied by determining the extravasation of Evans blue in the lungs and liver.
Fig. 3 shows a representative experiment
in which the wild-type (B/6+/+) mice displayed
significant VLS following IL-2 administration in the lungs and liver
compared with the PBS-treated group. However, in the CD44 KO mice,
there was a statistically significant decrease in VLS in the lungs and
liver. These experiments were repeated three times with consistent
results. These data suggested that CD44 may play a key role in the
induction of VLS in the lung and liver.
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Inasmuch as CD44 is involved in lymphocyte homing to organs,
histopathologic studies were conducted to investigate whether the
decrease in VLS in CD44 KO mice was due to the inability of the
lymphocytes to migrate to the lungs and liver. Mice were injected with
PBS or IL-2 as described in Fig. 3
. On day 4 the organs were harvested
and stained with hematoxylin and eosin. The PBS-treated mice did not
exhibit any perivascular infiltration in the lungs and liver (Fig. 4). In contrast, IL-2 treated wild-type
mice exhibited significant perivascular lymphocytic infiltration in the
lungs (Fig. 4) and liver (Fig. 5),
consistent with our earlier studies (12). It should be
noted that the infiltration was seen only around venules, but not
around arteries or arterioles. The IL-2-treated CD44 KO mice exhibited
similar levels of perivascular infiltration as the IL-2-treated
wild-type mice. The degree of infiltration was also measured by
counting the number of lymphocytes infiltrating each vessel and
averaging the range for each group (Table I). These results showed that
IL-2-treated wild-type and CD44 KO mice had similar levels of
perivascular infiltration. These data suggested that the decrease in
IL-2-induced VLS seen in CD44 KO mice was not due to the inability of
lymphocytes to migrate to the lungs and liver. IL-2 treatment also
caused an increase in the density expression of LFA-1 in the
lymphocytes (data not shown). It should be noted that the percentages
of CD4+ and CD8+ T cells in
wild-type and CD44 KO mice were similar before IL-2 treatment. Also
after IL-2 treatment, there was a similar increase in the percentage of
CD8+ T cells and a decrease in the percentage of
CD4+ T cells in wild-type and CD44 KO mice (data
not shown) as seen in our earlier study on wild-type mice
(12).
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To further corroborate that IL-2-induced VLS resulted from actual
damage to the endothelial cells, ultrastructural studies of the lung
(Fig. 6) and liver (Fig. 7) were performed. As shown in Fig. 6
(panel 1), lungs from wild-type mice injected with
PBS (control) displayed no morphological indications of damage to the
endothelial cells. Similar results were seen in lungs of
PBS-treated CD44 KO mice (Fig. 6, panel 3). In contrast,
following injection with IL-2, the wild-type mice demonstrated
extensive damage to the basal lamina and endothelial cells (Fig. 6, panel 2). Cellular debris from endothelial cells was found
in the blood capillary lumen. Some of the endothelial cells were
severely damaged, with only extended cell membrane remnants remaining
(Fig. 6, panel 2). In contrast to the wild-type mice,
IL-2-treated CD44 KO mice exhibited morphologically normal endothelial
cells pressed against the basal lamina in the lungs (Fig. 6, panel 4). The endothelial cells had intact organelles, and
very few morphological differences could be seen between the
IL-2-treated (Fig. 6, panel 4) and control tissues from CD44
KO mice (Fig. 6, panel 3).
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, panel 1) and CD44 KO (Fig. 7, panel 3) mice
showed no significant damage to the endothelial cells. There was
extensive damage to the endothelial cells in the livers of wild-type
mice treated with IL-2, resulting in their destruction and
cellular debris in the lumen (Fig. 7, panel 2). Only
remnants of the basal lamina were present. However, in
IL-2-treated CD44 KO mice, there was no endothelial cell damage in the
liver (Fig. 7, panel 4), and the tissue resembled the
control tissues (Fig. 7, panel 3). These results
corroborated the earlier observation that IL-2 treatment induces marked
VLS in wild-type, but not CD44 KO, mice (Fig. 3). Also, the VLS data
correlated with the actual damage to the endothelial cells. Adoptive transfer of CD44+, but not CD44-, spleen cells along with IL-2 triggers VLS in CD44 KO mice
Although the decreased VLS seen in CD44 KO mice suggested an
incriminatory role of CD44, it was not clear whether it could be
attributed to the deficiency of CD44 on immune cells or nonimmune
cells, including the endothelial cells. To address this, 2 x
108 spleen cells from CD44+
wild-type or CD44 KO mice were injected into CD44 KO mice, which also
received IL-2, as described in Fig. 3. Next, VLS was measured in the
lungs and liver. The data shown in Fig. 8
demonstrated that transfer of only CD44+, but not
CD44-, spleen cells into IL-2-treated CD44-KO
mice induced VLS in the lungs and liver. These data indicated that CD44
expression on immune cells was directly responsible for VLS
induction.
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To further confirm the role of CD44 in VLS, C57BL/6 wild-type mice
were treated with IL-2 and 100 µg F(ab')2 of
Abs against CD44 (IM7) or IL-2 and with rat IgG as a control. As shown
in Fig. 9A, injection of
F(ab')2 of Abs against CD44 significantly
inhibited VLS in the lung and liver compared with the VLS in mice
injected with IL-2 and control Abs. The inhibition caused by
anti-CD44 in VLS was dose dependent as shown in Fig. 9. For
example, in a similar experiment using 500 µg of
F(ab')2 of Abs against CD44 (Fig. 9B)
we noted a greater inhibition of VLS in the lungs and liver compared
with the controls. These data further support a role for CD44 in the
induction of VLS.
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Previous studies from our laboratory and elsewhere have suggested
that activated CTL and NK cells can use CD44 to kill the target cells
(9, 10, 17, 18). We therefore investigated the LAK
activity in CD44 KO mice. Splenic T cells were cultured with IL-2 and
after 48 h tested for LAK activity against P815, an NK-resistant
target. We noted that IL-2-activated LAK cells from CD44-KO mice
exhibited decreased ability to kill P815 compared with the wild-type
mice (Fig. 10A). We also
tested whether CD44 expression on LAK cells was required for activation
to the cytolytic phenotype or whether CD44 played an important role
during the effector phase in mediating the cytotoxicity. To this end,
spleen cells from CD44 wild-type mice were cultured with IL-2 to
generate LAK cells in the presence of Abs against CD44. In addition,
some spleen cells from CD44 wild-type mice were cultured with IL-2
alone to generate LAK cells. Subsequently, when testing the cytolytic
activity of such LAK cells against P815 target cells, they were
cultured in the presence of anti-CD44 mAbs. In the above studies
normal rat IgG was used as a control for anti-CD44 mAbs. The data
shown in Fig. 10B indicated that the presence of
anti-CD44 mAbs during the generation of LAK cells did not influence
the level of LAK activity. In contrast, addition of anti-CD44 mAbs
during the cytotoxicity testing blocked significantly LAK activity
(Fig. 10C). These data together demonstrated that CD44
expression played a critical role at the effector phase of LAK cell
function rather than at the differentiation phase.
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Discussion |
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TopAbstractIntroductionMaterials and MethodsResultsDiscussionReferences |
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There are many disease models in which factors other than cytolytic lymphocytes have been shown to participate in endothelial cell injury, including neutrophils and complement components (19). However, there is growing evidence for the involvement of cytolytic lymphocytes in endothelial cell injury. For example, IL-2-activated T cells and other leukocytes have been shown kill endothelial cells (20, 21, 22, 23, 24). Also, IL-2-induced VLS was seen only in immunocompetent, not in nude or immunodeficient, mice (25, 26). Furthermore, depletion of NK/LAK cells in vivo led to decreased toxicity during IL-2 therapy (27). Studies from our laboratory demonstrated that administration of a CTL clone plus IL-2 into irradiated syngeneic mice, but not the CTL clone or IL-2 alone, triggered VLS (21). Moreover, we have demonstrated that perforin-deficient or Fas ligand-defective mice exhibit decreased VLS in the lungs and liver following IL-2 therapy (12). Although all the studies mentioned above indicate the role of cytotoxic lymphocytes in endothelial cell injury and consequent induction of VLS, the exact mechanism of endothelial cell damage is not clear.
We and others have shown that activated CTL, NK cells, and double-negative T cells found in mice with the lpr mutation mediate efficient lysis of target cells when activated through CD44 (10, 11, 18). Inasmuch as, endothelial cells express the ligands for CD44, it is likely that dysregulated interaction between cytotoxic lymphocytes and endothelial cells can cause endothelial cell lysis. The current study supports this hypothesis. IL-2 treatment activates the LAK cells to express higher levels of perforin and Fas ligand as well as CD44, which may account for their ability to migrate to various organs and cause endothelial cell lysis (12, 28).
It is likely that CTL/LAK-induced endothelial cell damage may occur at sites of chronic inflammation or following cytokine therapy, but not during normal immune responses. This can be explained by regulatory mechanisms operating in vivo during the normal immune response. First, CD44 expression is up- or down-regulated based on the stage of activation of lymphocytes. Secondly, CD44 is expressed in a variety of isoforms, and therefore, the isoforms involved in cytotoxicity, homing, and adhesion may be different. Thirdly, CD44 and its ligand, HA, were found in soluble form in the serum and have been known to vary during disease conditions (10, 29). Such molecules may regulate the interactions between CTL and endothelial cells. Lastly, the interaction between Fas ligand and Fas expressed on cytotoxic lymphocytes and endothelial cells may regulate the degree of nonspecific cytotoxicity in vivo.
Although CD44 is known to play a wide variety of roles, mice deficient in CD44 do not exhibit developmental or neurological defects (13). However, such mice exhibit decreased LAK cell activity (30). This observation was confirmed in the current study, in which we noted that IL-2-activated LAK cells from CD44 mice, compared with those from wild-type mice, exhibited a marked decrease in their ability to kill NK-resistant P815 target cells. In the current study we noted that the IL-2-treated CD44 KO mice exhibited similar levels of perivascular infiltration with lymphocytes in the lungs and liver compared with wild-type mice. These data together suggested that the decreased VLS in CD44 KO mice resulted from the inability of LAK cells to mediate lysis of endothelial cells rather than the inability of lymphocytes to migrate and home to various organs. This was further corroborated by ultrastructural studies in which endothelial cells from CD44 KO mice showed normal morphology, unlike similar cells from wild-type mice, which exhibited marked damage. Recent studies have suggested that CD44 expressed by LAK cells may recognize HA on target cells to mediate cytotoxicity (30). In an earlier study we noted that B lymphocytes when activated with HA underwent proliferation and differentiation (16). In the current study we used CD44 KO mice to test whether such cells would exhibit decreased response to HA. The data demonstrated that the B cell responsiveness to HA in CD44 KO mice was significantly diminished, but not completely abrogated. These data further confirmed the role of CD44-hyaluronate interaction in lymphocyte activation. Also, because the responsiveness of B cells to HA in CD44 KO mice was not completely abolished, alternate receptors, such as CD38, may play a role in B cell activation (31).
In the current study although IL-2-induced VLS was used as a model to study endothelial cell damage, there are a number of clinical diseases in which similar endothelial cell injury has been reported. In murine lymphocytic choriomeningitis viral infection, a massive delayed-type hypersensitivity reaction has been known to occur in the nervous system, caused by CD8+ T cells (1). It has been speculated that virally activated CD8+ T cells expressing high levels of CD44, kill endothelial cells, leading to massive extravasation of monocytes and CD4+ T cells in the subarachnoid space. In autoimmune disease models involving vasculitides, the lesions are associated with infiltration of lymphocytes and macrophages at the vascular wall structure (3). The T cell involvement in the endothelial cell damage also leads to vascular disease in scleroderma (32). Moreover, the PBLs from some patients with rheumatoid arthritis and giant cell arthritidis have been shown to be cytotoxic to endothelial cells, but not to fibroblasts (33). Further studies in such disease models on the role of CD44 should help in understanding and preventing pathogenesis.
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Footnotes |
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2 Address correspondence and reprint requests to Dr. Prakash S. Nagarkatti, Department of Biology, Virginia Tech, Blacksburg, VA 24061. E-mail address:
3 Abbreviations used in this paper: VLS, vascular leak syndrome; ECM, extracellular matrix; HA, hyaluronic acid; KO, knockout; LAK cell, lymphokine-activated killer cell.
Received for publication December 16, 1998. Accepted for publication May 24, 1999.
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Q. Wang, P. Teder, N. P. Judd, P. W. Noble, and C. M. Doerschuk CD44 Deficiency Leads to Enhanced Neutrophil Migration and Lung Injury in Escherichia coli Pneumonia in Mice Am. J. Pathol., December 1, 2002; 161(6): 2219 - 2228. [Abstract] [Full Text] [PDF]
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R. J. McKallip, Y. Do, M. T. Fisher, J. L. Robertson, P. S. Nagarkatti, and M. Nagarkatti Role of CD44 in activation-induced cell death: CD44-deficient mice exhibit enhanced T cell response to conventional and superantigens Int. Immunol., September 1, 2002; 14(9): 1015 - 1026. [Abstract] [Full Text] [PDF]
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M. I. Tammi, A. J. Day, and E. A. Turley Hyaluronan and Homeostasis: A Balancing Act J. Biol. Chem., February 8, 2002; 277(7): 4581 - 4584. [Full Text] [PDF]
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E. A. Turley, P. W. Noble, and L. Y. W. Bourguignon Signaling Properties of Hyaluronan Receptors J. Biol. Chem., February 8, 2002; 277(7): 4589 - 4592. [Full Text] [PDF]
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 G. Sconocchia, L. Campagnano, D. Adorno, A. Iacona, N. Y. Cococcetta, V. Boffo, S. Amadori, and C. U. Casciani CD44 ligation on peripheral blood polymorphonuclear cells induces interleukin-6 production Blood, June 1, 2001; 97(11): 3621 - 3627. [Abstract] [Full Text] [PDF]
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D. Chen, R. J. McKallip, A. Zeytun, Y. Do, C. Lombard, J. L. Robertson, T. W. Mak, P. S. Nagarkatti, and M. Nagarkatti CD44-Deficient Mice Exhibit Enhanced Hepatitis After Concanavalin A Injection: Evidence for Involvement of CD44 in Activation-Induced Cell Death J. Immunol., May 15, 2001; 166(10): 5889 - 5897. [Abstract] [Full Text] [PDF]
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S. L. Blass, E. Pure, and C. A. Hunter A Role for CD44 in the Production of IFN-{{gamma}} and Immunopathology During Infection with Toxoplasma gondii J. Immunol., May 1, 2001; 166(9): 5726 - 5732. [Abstract] [Full Text] [PDF]
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