Table II.

Effect of IFN-γ pretreatment of SW480 and SW620 colon carcinoma cells on effector cell-target cell conjugate formation

Tumor Cell LineIFN-γ (+/–)aCTLbAbc% Conjugatesd
SW480 ras None4.4 ± 0.03
MART-1None4.9 ± 0.03
SW480+ ras None35.4 ± 0.6
+ ras Anti-ICAM-14.5 ± 0.2
+ ras Isotype35.2 ± 1.8
+MART-1None4.2 ± 0.1
SW620 ras None5.7 ± 0.3
MART-1None2.9 ± 0.9
SW620+ ras None30.6 ± 1.4
+ ras Anti-ICAM-15.2 ± 0.8
+ ras Isotype38.1 ± 1.4
+MART-1None3.9 ± 0.5
  • a Tumor cells, untreated (–) or pretreated (+) with IFN-γ, as described in Table I and Fig. 2, were then labeled with a red fluorescent marker (PKH26).

  • b Anti-ras 4-12(Val12) CTL or anti-MART-127–35 CTL were prelabeled with a green fluorescent marker (BCECF).

  • c Anti-ICAM-1 or isotype control (MOPC-21) (10 μg/ml) were included in the assay.

  • d After incubation, cell suspensions (E:T ratio, 2:1) were immediately analyzed by flow cytometry for dual expression of BCECF+ PKH26+ events within the PKH26+ population. Additional controls included tumor cells 1) incubated in the absence of effectors; and 2) mixed with relevant effectors (ras CTL), but analyzed immediately without prior incubation. Under those conditions, two-color staining was <4%. The data were expressed as the mean ± SEM of triplicate tubes/group and are representative of three separate experiments.