|
|
||||||||
CUTTING EDGE |
Department of Immunology, Imperial College School of Medicine, Hammersmith Hospital, London, United Kingdom
| Abstract |
|---|
|
|
|---|
| Introduction |
|---|
|
|
|---|
CD2, the prototype of the family, is a transmembrane protein expressed on the surface of T lymphocytes, thymocytes, and NK cells; in mice, it is also found on B cells (1). CD2 has two known ligands. Its major ligand in humans is CD58 (LFA-3) (2), a molecule that is widely expressed on hemopoietic and many nonhemopoietic tissues. No CD58 homologue has been identified in rodents. Instead, another member of the CD2 subfamily, CD48 (3, 4, 5, 6) has been identified as a CD2 ligand in mice and rats (1). The expression of CD48 is regulated more tightly than that of CD58 and is restricted to lymphocytes, dendritic cells, and macrophages (1).
The functional significance of murine CD2 and CD48 is still uncertain. Mice carrying a targeted mutation in the Cd2 gene are almost normal phenotypically (1). In contrast, the phenotype of CD48-deficient mice that we have recently generated is more pronounced. Specifically, T lymphocytes from CD48-deficient mice are impaired in activation (Cabrero et al., manuscript in preparation). This discrepancy in phenotypes led us to ask whether CD48 binds to another counter-receptor in addition to CD2. In this article we provide evidence that CD48 binds the 2B4 molecule.
| Materials and Methods |
|---|
|
|
|---|
The following mAbs and second-step reagents were obtained from PharMingen (San Diego, CA): anti-mouse CD2 (clone RM2-5), anti-mouse CD48 (clone HM48.1), anti-mouse 2B4 (clone 2B4), anti-Thy-1 mAb (clone 53-2.1), and FITC-avidin. Anti-glycoprotein 200 (gp200)-MR6 (clone MR6 (7)) and anti-H-2Kb (clone Y3 (8)) mAbs were gifts of Drs. Mary Ritter and Hans Stauss (Hammersmith Hospital), respectively. The human CTLA4-Ig fusion protein has been described previously (9). All other Abs and chemicals were obtained from Sigma (Dorset, U.K.) unless otherwise indicated.
Construction of CD48-Ig fusion protein
CD48 was amplified by PCR from a B cell cDNA library (6). The sense primer (5'-TGGGAAAGCTTTTTCAAGGTCATTCAATACCAG-3') corresponds to base pairs 6788 of CD48 and to a restriction site for HindIII. The antisense primer (5'-GAAGGGATCCCCTAGATCACAAGGTAGAGTGAAGTACAC-3') corresponded to nucleotides 616643 of CD48 and to a restriction site for BamHI. PCR conditions were 94°C for 1 min, primer annealing at 55°C for 1 min, and an extension at 72°C for 1 min, for 35 cycles. The 598-bp product was digested with HindIII and BamHI and ligated into the signal pIg plus vector that contains the signal peptide of CD33 and the human IgG1 Fc fragment (Ingenius, Abingdon, U.K.). The sequence of the resulting plasmid was confirmed by MWG-Biotech (Milton Keynes, U.K.).
COS-7 cells were transfected with the CD48-pIg plasmid using Lipofectin (Life Technologies, Paisley, UK). Transfected cells were selected with 1 mg/ml of G418 and subcloned. The CD48-Ig protein was purified from culture medium on a protein A column and subjected to Western blot analysis. For this purpose, samples (1 µg) of the CD48-Ig fusion protein or of a gp200-MR6 control fusion protein (P.F.M. and M. Ritter, unpublished observations) were fractionated on a 7.5% SDS-PAGE gel under nonreducing conditions. Following electrophoresis, proteins were transferred onto polyvinylidene difluoride (PVDF) membranes. Following a blocking step, membranes were cut; the pieces were subjected to one of the following incubations as described previously (10): 1) biotinylated goat anti-human IgG followed by avidin peroxidase (extravidin peroxidase); 2) biotinylated hamster anti-mouse CD48 followed by avidin-peroxidase; or 3) mouse anti-human gp200-MR6 Ab followed by peroxidase-labeled rabbit anti-mouse Ig. Membranes were washed after each incubation. Proteins were visualized with enhanced chemiluminescence (ECL) substrate (Amersham, Little Chalfont, U.K.) before autoradiography.
Immunofluorescence and flow cytometry
To determine CD2 expression, cells were incubated with biotinylated anti-CD2 mAb (clone RM2-5) followed by incubation with FITC-avidin. To determine 2B4 expression, cells were incubated with anti-2B4 mAb (clone 2B4) followed by incubation with FITC-conjugated goat anti-mouse IgG. For staining with CD48-Ig or CTLA4-Ig, cells were incubated with purified fusion protein followed by incubation with biotin-conjugated goat anti-human IgG and, finally, by incubation with FITC-avidin. Control stainings included stainings with developing reagents (biotin-conjugated goat anti-human IgG followed by FITC-avidin; FITC-conjugated goat anti-mouse Ig) only. For the sake of clarity, the staining profiles of these control stainings are omitted in several of the figures. All incubations were conducted on ice. Following each step, cells were washed three times with PBS/1% BSA before the next incubation. After the final incubation, cells were washed and fixed with 1% paraformaldehyde. Samples were analyzed on a Coulter Epics XL-MCL instrument (Hialeah, FL). A total of 10,000 cells were analyzed per sample.
Cloning and expression of murine 2B4
The complete coding region of 2B4 was amplified by PCR from
CTLL-2 cells and cloned into the pEGFP-C1-NotI vector
(Clontech, Palo Alto, CA). The sense primer was
5'-GTAGGCGGCCGCGTCCTGTGGTGATGTTGGGGCAAGCTG-3' and corresponded to
base pairs 116 of 2B4 and a restriction site for NotI. The
antisense primer was 5'-GCGAATTCCTAGGAGTAGACATCAAAGTTCTCCAGCTCTC-3'
and consisted of nucleotides 11661197 of 2B4 and a restriction site
for EcoRI. PCR conditions were 94°C for 1 min, primer
annealing at 65°C for 1 min, and an extension at 72°C for 1 min,
for 35 cycles. The 1.23-kb NotI/EcoRI-digested
PCR product was ligated into the pEGFP-C1-NotI vector that
had been digested with NotI and EcoRI to remove
the green fluorescent protein. The resulting construct, termed 2B4-pYL,
was used to transform DH5
cells. COS-7 cells were transfected with
2B4-pYL DNA by electroporation. As a control, COS-7 cells were
transfected with the cDNA encoding the gp200-MR6 Ag cloned into the
identical expression vector (P.F.M., unpublished observations). Cells
were incubated for 48 h to allow transient expression.
Immunoprecipitations
Cell surface proteins were biotinylated with sulfo-N-hydroxysuccinimide-biotin (Pierce, Rockford, IL) according to the manufacturers instructions. Cell lysates were prepared and immunoprecipitations were conducted as described previously (6). Proteins were separated by SDS-PAGE as described previously (6), except that a separating gel with an acrylamide/bisacrylamide ratio of 30:0.8 was used in the fractionation.
| Results |
|---|
|
|
|---|
A plasmid encoding a fusion protein comprising the extracellular
domain of CD48 and the C region of human IgG1 was constructed as
detailed in Materials and Methods. This construct, termed
CD48-pIg, was introduced into COS-7 cells by lipofection.
G418-resistant cells were selected, and CD48-Ig fusion protein was
subsequently purified from culture supernatants on a protein A column.
The presence of fusion protein was confirmed by Western blot analysis
(Fig. 1
). The purified protein was
recognized by anti-human IgG and anti-mouse CD48 Abs (Fig. 1
, left and middle panels) but not by an irrelevant
control (anti-gp200-MR6) Ab (Fig. 1
, right panel).
|
To assess the usefulness of the CD48-Ig fusion protein, we
initially analyzed stable CD2 transfectants by immunofluorescence and
flow cytometry. As shown in Fig. 2
A, CD48-Ig recognizes CD2.
This staining was specific, because no reactivity was observed with
control transfectants (data not shown). To search for a CD48
counter-receptor distinct from CD2, we subsequently screened a panel of
cell lines for reactivity with anti-CD2 mAb and CD48-Ig. As
shown in Fig. 2
B, CTLL-2 cells do not express CD2 on the
cell surface. In contrast, these cells can be stained with the CD48-Ig
fusion protein. Staining with this reagent was specific, because a
control fusion protein, CTLA4-Ig, did not react with CTLL-2 cells (Fig. 2
B). Additional staining analyses revealed that CTLL cells
express the 2B4 Ag on the cell surface (Fig. 2
B). Because
2B4 and CD2 belong to the same subfamily of the IgSF and are both
composed of a single V-set domain and a single C2-set domain, 2B4 was a
good candidate to be a second counter-receptor of CD48.
|
To investigate whether 2B4 was a counter-receptor for CD48, we
initially determined the apparent molecular mass of the Ag
recognized by CD48-Ig on CTLL-2 cells. The apparent molecular
mass of the 2B4 Ag has been studied previously and was
determined to be 66 kDa (11). To determine the apparent molecular mass
of the Ag recognized by CD48-Ig fusion protein, we conducted
immunoprecipitations on detergent lysates derived from
surface-biotinylated CTLL-2 cells. As shown in Fig. 2
C, the
CD48-Ig fusion protein specifically immunoprecipitated a major band of
66 kDa from CTLL-2 cells. The band comigrates with the protein
immunoprecipitated by anti-2B4 mAb (Fig. 2
C). This
result strongly suggested that 2B4 was a counter-receptor for CD48. To
test this hypothesis directly, we employed sequential
immunoprecipitation studies on lysates from CTLL-2 cells. The results
of these experiments revealed that the preclearing immunoprecipitations
with anti-2B4 mAb eliminated the band immunoprecipitated by CD48-Ig
(Fig. 2
D).
CD48-Ig stains 2B4 transfectants
To independently demonstrate the CD482B4 interaction, we
examined whether CD48-Ig could recognize the 2B4 expressed on specific
transfectants. For this purpose, we cloned the 2B4 cDNA into an
expression vector for use in gene transfection experiments. COS-7 cells
were transfected with this plasmid by electroporation as described in
Materials and Methods. Cells were incubated for 48 h to
allow transient expression. After the incubation period, the cell
surface expression of Ags was studied by indirect immunofluorescence
and flow cytometry. Fig. 3
shows a
representative experiment. As shown in Fig. 3
A, the CD48-Ig
fusion protein reacts with the product of the 2B4 cDNA clone in
transfected COS-7 cells. Two findings support the specificity of
this result. First, a control fusion protein, CTLA4-Ig, did not
react with the 2B4-transfected cell (Fig. 3
A). This latter
reagent recognizes B7-1 transfectants (ref. 9 and data not shown).
Second, the CD48-Ig fusion protein did not react with COS-7 cells that,
as a control, had been transfected with the cDNA (P.F.M. and M. Ritter,
unpublished observations) encoding the human gp200-MR6 Ag (Fig. 3
B). Taken together, our data demonstrate that the
CD48-Ig fusion protein recognizes the 2B4 Ag on the surface of
2B4-transfected COS-7 cells, and that 2B4 is a counter-receptor for
CD48.
|
| Discussion |
|---|
|
|
|---|
Like CD48, the 2B4 Ag belongs to the CD2 subfamily of the IgSF. Indeed, 2B4, CD2, and CD48 show significant homology (1, 12), and all comprise a V-set domain as well as a C2-set domain. Therefore, the CD48 molecule as well as both of its known ligands (CD2 and 2B4) have similar primary structure, similar overall structure, and are evolutionarily related. Our finding that CD48 and 2B4 can interact is consistent with the model developed by Davis and van der Merwe (1) who have analyzed the binding characteristics of the CD2-CD48 interaction.
The 2B4 molecule, which is expressed on NK cells, T cells mediating
non-MHC-restricted cytotoxicity, and murine epidermal 
T cells,
has been found to transduce activation signals (11, 13). Most
importantly, NK cells and 
T cells express critical effector and
regulatory functions. For example, NK cells can interact with and
stimulate T and B lymphocytes, and these interactions are known to
require cell to cell contact (14, 15). Because CD48 is expressed on T
and B cells as well as on dendritic cells, the binding of 2B4 to CD48
may participate in a variety of cell to cell interactions that are
important for immune responses. Future studies are needed to explore
this possibility.
| Acknowledgments |
|---|
| Footnotes |
|---|
2 Address correspondence and reprint requests to Dr. Hans Reiser, Department of Immunology, Imperial College School of Medicine, Hammersmith Hospital, Du Cane Road, London W12 0NN, U.K. ![]()
3 Abbreviations used in this paper: IgSF, Ig superfamily; ECL, enhanced chemiluminescence; gp, glycoprotein; PVDF, polyvinylidene difluoride. ![]()
Received for publication August 26, 1998. Accepted for publication September 29, 1998.
| References |
|---|
|
|
|---|

T cells through surface 2B4. Eur. J. Immunol. 25:1117.[Medline]
This article has been cited by other articles:
![]() |
L. K. Chlewicki, C. A. Velikovsky, V. Balakrishnan, R. A. Mariuzza, and V. Kumar Molecular Basis of the Dual Functions of 2B4 (CD244) J. Immunol., June 15, 2008; 180(12): 8159 - 8167. [Abstract] [Full Text] [PDF] |
||||
![]() |
J. A. Wahle, K. H. T. Paraiso, R. D. Kendig, H. R. Lawrence, L. Chen, J. Wu, and W. G. Kerr Inappropriate Recruitment and Activity by the Src Homology Region 2 Domain-Containing Phosphatase 1 (SHP1) Is Responsible for Receptor Dominance in the SHIP-Deficient NK Cell J. Immunol., December 15, 2007; 179(12): 8009 - 8015. [Abstract] [Full Text] [PDF] |
||||
![]() |
P. Vacca, G. Pietra, M. Falco, E. Romeo, C. Bottino, F. Bellora, F. Prefumo, E. Fulcheri, P. L. Venturini, M. Costa, et al. Analysis of natural killer cells isolated from human decidua: evidence that 2B4 (CD244) functions as an inhibitory receptor and blocks NK-cell function Blood, December 15, 2006; 108(13): 4078 - 4085. [Abstract] [Full Text] [PDF] |
||||
![]() |
R. Bhat, P. Eissmann, J. Endt, S. Hoffmann, and C. Watzl Fine-tuning of immune responses by SLAM-related receptors J. Leukoc. Biol., March 1, 2006; 79(3): 417 - 424. [Abstract] [Full Text] [PDF] |
||||
![]() |
Y. T. Bryceson, M. E. March, D. F. Barber, H.-G. Ljunggren, and E. O. Long Cytolytic granule polarization and degranulation controlled by different receptors in resting NK cells J. Exp. Med., October 3, 2005; 202(7): 1001 - 1012. [Abstract] [Full Text] [PDF] |
||||
![]() |
E. Assarsson, T. Kambayashi, C. M. Persson, B. J. Chambers, and H.-G. Ljunggren 2B4/CD48-Mediated Regulation of Lymphocyte Activation and Function J. Immunol., August 15, 2005; 175(4): 2045 - 2049. [Abstract] [Full Text] [PDF] |
||||
![]() |
M. Martin, J. M. Del Valle, I. Saborit, and P. Engel Identification of Grb2 As a Novel Binding Partner of the Signaling Lymphocytic Activation Molecule-Associated Protein Binding Receptor CD229 J. Immunol., May 15, 2005; 174(10): 5977 - 5986. [Abstract] [Full Text] [PDF] |
||||
![]() |
S. V. Vaidya, S. E. Stepp, M. E. McNerney, J.-K. Lee, M. Bennett, K.-M. Lee, C. L. Stewart, V. Kumar, and P. A. Mathew Targeted Disruption of the 2B4 Gene in Mice Reveals an In Vivo Role of 2B4 (CD244) in the Rejection of B16 Melanoma Cells J. Immunol., January 15, 2005; 174(2): 800 - 807. [Abstract] [Full Text] [PDF] |
||||
![]() |
A. Munitz, I. Bachelet, S. Fraenkel, G. Katz, O. Mandelboim, H.-U. Simon, L. Moretta, M. Colonna, and F. Levi-Schaffer 2B4 (CD244) Is Expressed and Functional on Human Eosinophils J. Immunol., January 1, 2005; 174(1): 110 - 118. [Abstract] [Full Text] [PDF] |
||||
![]() |
J. M. Mooney, J. Klem, C. Wulfing, L. A. Mijares, P. L. Schwartzberg, M. Bennett, and J. D. Schatzle The Murine NK Receptor 2B4 (CD244) Exhibits Inhibitory Function Independent of Signaling Lymphocytic Activation Molecule-Associated Protein Expression J. Immunol., September 15, 2004; 173(6): 3953 - 3961. [Abstract] [Full Text] [PDF] |
||||
![]() |
R. Chen, F. Relouzat, R. Roncagalli, A. Aoukaty, R. Tan, S. Latour, and A. Veillette Molecular Dissection of 2B4 Signaling: Implications for Signal Transduction by SLAM-Related Receptors Mol. Cell. Biol., June 15, 2004; 24(12): 5144 - 5156. [Abstract] [Full Text] [PDF] |
||||
![]() |
R. M. Flaig, S. Stark, and C. Watzl Cutting Edge: NTB-A Activates NK Cells via Homophilic Interaction J. Immunol., June 1, 2004; 172(11): 6524 - 6527. [Abstract] [Full Text] [PDF] |
||||
![]() |
K.-M. Lee, M. E. McNerney, S. E. Stepp, P. A. Mathew, J. D. Schatzle, M. Bennett, and V. Kumar 2B4 Acts As a Non-Major Histocompatibility Complex Binding Inhibitory Receptor on Mouse Natural Killer Cells J. Exp. Med., May 3, 2004; 199(9): 1245 - 1254. [Abstract] [Full Text] [PDF] |
||||
![]() |
G. Ferlazzo and C. Munz NK Cell Compartments and Their Activation by Dendritic Cells J. Immunol., February 1, 2004; 172(3): 1333 - 1339. [Full Text] [PDF] |
||||
![]() |
S. Dhanji and H.-S. Teh IL-2-Activated CD8+CD44high Cells Express Both Adaptive and Innate Immune System Receptors and Demonstrate Specificity for Syngeneic Tumor Cells J. Immunol., October 1, 2003; 171(7): 3442 - 3450. [Abstract] [Full Text] [PDF] |
||||
![]() |
C. Watzl and E. O. Long Natural Killer Cell Inhibitory Receptors Block Actin Cytoskeleton-dependent Recruitment of 2B4 (CD244) to Lipid Rafts J. Exp. Med., January 6, 2003; 197(1): 77 - 85. [Abstract] [Full Text] [PDF] |
||||
![]() |
D. Howie, S. Okamoto, S. Rietdijk, K. Clarke, N. Wang, C. Gullo, J. P. Bruggeman, S. Manning, A. J. Coyle, E. Greenfield, et al. The role of SAP in murine CD150 (SLAM)-mediated T-cell proliferation and interferon gamma production Blood, September 26, 2002; 100(8): 2899 - 2907. [Abstract] [Full Text] [PDF] |
||||
![]() |
T. Kambayashi, E. Assarsson, B. J. Chambers, and H.-G. Ljunggren Cutting Edge: Regulation of CD8+ T Cell Proliferation by 2B4/CD48 Interactions J. Immunol., December 15, 2001; 167(12): 6706 - 6710. [Abstract] [Full Text] [PDF] |
||||
![]() |
S. S. Chuang, P. R. Kumaresan, and P. A. Mathew 2B4 (CD244)-Mediated Activation of Cytotoxicity and IFN-{gamma} Release in Human NK Cells Involves Distinct Pathways J. Immunol., December 1, 2001; 167(11): 6210 - 6216. [Abstract] [Full Text] [PDF] |
||||
![]() |
M. Martin, X. Romero, M. A. de la Fuente, V. Tovar, N. Zapater, E. Esplugues, P. Pizcueta, J. Bosch, and P. Engel CD84 Functions as a Homophilic Adhesion Molecule and Enhances IFN-{gamma} Secretion: Adhesion Is Mediated by Ig-Like Domain 1 J. Immunol., October 1, 2001; 167(7): 3668 - 3676. [Abstract] [Full Text] [PDF] |
||||
![]() |
G. A. Kingsbury, L. A. Feeney, Y. Nong, S. A Calandra, C. J. Murphy, J. M. Corcoran, Y. Wang, M. R. Prabhu Das, S. J. Busfield, C. C. Fraser, et al. Cloning, Expression, and Function of BLAME, a Novel Member of the CD2 Family J. Immunol., May 1, 2001; 166(9): 5675 - 5680. [Abstract] [Full Text] [PDF] |
||||
![]() |
J. Sayos, K. B. Nguyen, C. Wu, S. E. Stepp, D. Howie, J. D. Schatzle, V. Kumar, C. A. Biron, and C. Terhorst Potential pathways for regulation of NK and T cell responses: differential X-linked lymphoproliferative syndrome gene product SAP interactions with SLAM and 2B4 Int. Immunol., December 1, 2000; 12(12): 1749 - 1757. [Abstract] [Full Text] [PDF] |
||||
![]() |
C. Watzl, C. C. Stebbins, and E. O. Long Cutting Edge: NK Cell Inhibitory Receptors Prevent Tyrosine Phosphorylation of the Activation Receptor 2B4 (CD244) J. Immunol., October 1, 2000; 165(7): 3545 - 3548. [Abstract] [Full Text] [PDF] |
||||
![]() |
L. Benoit, X. Wang, H. F. Pabst, J. Dutz, and R. Tan Cutting Edge: Defective NK Cell Activation in X-Linked Lymphoproliferative Disease J. Immunol., October 1, 2000; 165(7): 3549 - 3553. [Abstract] [Full Text] [PDF] |
||||
![]() |
S. Parolini, C. Bottino, M. Falco, R. Augugliaro, S. Giliani, R. Franceschini, H. D. Ochs, H. Wolf, J.-Y. Bonnefoy, R. Biassoni, et al. X-Linked Lymphoproliferative Disease: 2b4 Molecules Displaying Inhibitory Rather than Activating Function Are Responsible for the Inability of Natural Killer Cells to Kill Epstein-Barr Virus-Infected Cells J. Exp. Med., August 7, 2000; 192(3): 337 - 346. [Abstract] [Full Text] [PDF] |
||||
![]() |
J. Gonzalez-Cabrero, C. J. Wise, Y. Latchman, G. J. Freeman, A. H. Sharpe, and H. Reiser CD48-deficient mice have a pronounced defect in CD4+ T cell activation PNAS, February 2, 1999; 96(3): 1019 - 1023. [Abstract] [Full Text] [PDF] |
||||
![]() |
M. Morra, M. Simarro-Grande, M. Martin, A. S.-I. Chen, A. Lanyi, O. Silander, S. Calpe, J. Davis, T. Pawson, M. J. Eck, et al. Characterization of SH2D1A Missense Mutations Identified in X-linked Lymphoproliferative Disease Patients J. Biol. Chem., September 21, 2001; 276(39): 36809 - 36816. [Abstract] [Full Text] [PDF] |
||||
| |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| HOME | HELP | FEEDBACK | SUBSCRIPTIONS | ARCHIVE | SEARCH | TABLE OF CONTENTS |