COMPARATIVE-ANALYSIS OF CD8 EXPRESSED ON MATURE CD4+CD8+ T-CELL CLONES CULTURED WITH IL-4 AND THAT ON CD8+ T-CELL CLONES - IMPLICATION FOR FUNCTIONAL-SIGNIFICANCE OF CD8-BETA

Interleukin (IL-4) can induce CD8 expression on mature CD4+ T cells. To study this phenomenon in more detail, we characterized CD8 expressed on IL-4-induced CD4+CD8+ (double positive) T cell clones in comparison with that on CD8+ T cell clones. Using 2ST8-5H7 mAb that detects CD8-beta expression, we found that double positive T cell clones isolated with IL-4 express CD8-alpha but not beta, in contrast to CD8+ CTL cell clones, which express both chains of CD8. Northern blot analysis revealed that these double positive clones expressed CD8-alpha but not beta mRNA, indicating that CD8-alpha and beta are independently regulated at the pre-translational level. Immunoprecipitation experiments showed that CD8 expressed on a representative IL-4-induced double positive T cell clone consists mainly of homodimers of a single 34 kd protein of CD8-alpha. The amount of multimers detected from this clone was much less than that from a CD8+ CTL clone. These results suggest that persistent expression of CD8-beta is specific for the CD8+ lineage and may be involved in polymerization and stabilization of CD8 which enhances the efficiency of class I-restricted antigen recognition.