The functional heterogeneity of CD8+ cells defined by anti-CD45RA (2H4) and anti-CD29 (4B4) antibodies

The monoclonal antibodies, anti-2H4(CD45RA), and anti-4B4(CD29), along with UCHL1-(CD45RO), identify reciprocal populations of CD4 cells with distinct suppressor inducer (CD45RA+CD29-CD45RO-) and helper inducer (CD45RA-CD29+CD45RO+) functions. Although the CD8+ population is known to contain precytotoxic, cytotoxic, suppressor, and some natural killer cells, the exact phenotypic identities of these functional CD8 subsets has not been established. In this study, we tried to determine whether these monoclonal antibodies could distinguish functionally distinct subsets of cells within the CD8+ population. For this purpose, whole T cells or fractionated T cells were sensitized with irradiated allogeneic non-T cells for 6 days, following which, CD8+ or CD8+CD11b- cells were isolated and cellular functions such as suppressor, killer precursor, and killer effector activity were assessed. The results showed that both class I-restricted alloantigen-specific killer effector and killer precursor cells belonged to the CD8+CD11b-CD45RA-CD29+ population. Moreover, these killer effector cells expressed the CTL-associated S6F1 molecule, an epitope of the LFA-1 antigen. In contrast, suppressor effector cells belonged to the CD8+CD11b-CD45RA+CD29- cell population. Although the UCHL1 antigen has been reported to define the CD4+CD29+ helper inducer cell, over 90% of allo-activated CD8+ cells expressed this antigen, whereas only 40-60% of these cells expressed either CD45RA or CD29 antigens. These results suggest that anti-CD45RA and anti-CD29 antibodies may provide useful tools for distinguishing between suppressor effector versus killer effector and killer precursor cells within the CD8+CD11b- population.