Recruitment of effector lymphocytes by initiator lymphocytes: role of a trypsin-sensitive membrane component.

In earlier studies we found that initiator T lymphocytes sensitized in vitro against fibroblasts were able to recruit immunospecific effector T lymphocytes in vivo in syngeneic mice. In the present study, to investigate the possible function in effector cell recruitment of sensitizing antigens passively adsorbed onto the initiator cell membrane, we treated the initiator lymphocytes with trypsin. We found that trypsin inhibited recruitment. However, the initiator cells spontaneously recovered their recruiting ability after incubation in vitro for 4 h in the absence of contact with sensitizing antigens. Recovery could be blocked by cycloheximide. Hence, it appears that recruitment depends on the intrinsic metabolic function of the initiator lymphocytes and is not due merely to passively-adsorbed antigen carried over into the recipient mouse.