HLA Class II Defects in Burkitt Lymphoma: Bryostatin-1-Induced 17 kDa Protein Restores CD4+ T-Cell Recognition

Figure 3

Addition of external co-stimulation is not sufficient to overcome class II-associated defects in BL. BLs are known to express lower levels of costimulatory molecules, raising the possibility that this was the cause of the observed defect in their ability to present Ag via class II. BL cell lines Nalm-6.DR4 and Ramos.DR4, and the B-LCL cell line 6.16.DR4.DM were incubated with κI and κII peptides prior to co-culture with the T-cell hybridomas 2.18a or 1.21 which had been stimulated with anti-CD3/CD28. Culture supernatant was assayed by ELISA for IL-2 levels as a measure of T-cell stimulation. These results demonstrate that Nalm-6.DR4 and Ramos.DR4 Ag presentation is unaffected by the addition of external co-stimulation and remains deficient in class II-mediated presentation.