I-A antigens on cloned alloreactive murine T lymphocytes are acquired passively.

Cloned lines of alloreactive cytolytic and amplifier T lymphocytes have been examined for expression of I-A antigens. Using flow cytofluorometry and monoclonal antibodies, MHC antigens representing both I-A and H-2K or D determinants were reproducibly detected on the cell surface of these cloned T lymphocytes. All cloned lines examined expressed H-2K or D antigens representing the MHC haplotype appropriate to their strain of origin. However, I-A as well as H-2K or D antigens appeared to be acquired passively from the stimulating cell population. Within the lower limits of detection using the fluorescence-activated cell sorter, evidence suggesting endogenous synthesis of I-A antigens by these cloned T lymphocytes could not be demonstrated. Further, the observed binding appeared to be nonspecific, because material originating from allogeneic, syngeneic, or third-party stimulating cells could be observed under appropriate conditions.