Several investigators have provided evidence that more than one Ly-1 T cell subset is involved in helper effector (HE) 1 function for the B cell response to T-dependent antigens. Distinctive functional Ly-1 subsets have been defined by additional phenotypic markers (notably I-A, I-J, and Qa-1) (1-5), adherence properties (3), priming environment (6-9), major histocompatibility complex restrictions (4), antigen specificity (4, 7), and theoretical interpretations of the slope of dose-response curves at limiting effector cell input (log antibody response vs. log effector cell number) (6, 7).This report resolves a major discrepancy we have had in relation to other reports as to whether or not the Qa-1 immunogenetic marker distinguishes two functional Ly-1: HE subsets. We find that isolated T cells primed with antigen-pulsed macrophages generate appreciable HE activity only in the Ly-1 :Qa-1-T cell subset. However, an Ly-l:Qa-I + T cell subset associated with HE function can be generated if priming takes place (in vivo or in vitro) in an environment containing B cells.
Materials and MethodsMice. C57BL/6 (B6) mice (H-2b:Lyt-l.2:Lyt-2.2:Qa-1 -) were obtained from The Jackson Laboratory (Bar Harbor, ME). Congenic B6-Tla a (H-2b:Lyt-l.2:Lyt-2.2:Qa-1 +) were bred at Sloan-Kettering Institute, New York.Antigens. Preparation of group A streptococcus vaccine (SAV) and its trinitrophenyl conjugate (TNP-SAV) is described elsewhere (10).SA V-primed Ly-I T Cells. The thymocyte-macrophage (T-Me) culture system, in which cortisone-resistant nylon-purified thymocytes (CRNPT) are cultured for 4 d on macrophages from SAV-primed donors, has been described in detail (11,12). This system yields mostly Ly-1 cells, which are harvested at 4 d, treated with anti-Lyt-2.2 serum plus complement (C), and assayed for HE activity by their effect on the anti-TNP-SAV plaque-forming cell (PFC) response of T-depleted spleen cell cultures from unprimed mice (10). Splenic T cells were primed in vitro either as the whole spleen cell population or as nylon wool-purified splenic T cells exactly as is done with CRNPT. Experiments reported here were done at least three times.