MEMORY IN HELPER T-CELLS OF MINOR HISTOCOMPATIBILITY ANTIGENS, REVEALED INVIVO BY ALLOIMMUNIZATIONS IN COMBINATION WITH THY-1 ANTIGEN

A cooperative antibody response in which T helper (T(h)) cells recognize minor histocompatibility antigens (mha) and B cells recognize Thy-1 antigen, is used to explore memory in the T cell compartment. In contrast to B cell memory, T(h) memory reaches a plateau rapidly, although T(h) memory of Thy-1 itself (or an associated antigen) behaves exceptionally in this respect. The plateau then extends over several weeks at least. Single mha, among them H-Y, generate detectable memory. Incompatible H-2 antigens, including class I antigens on their own, inhibit this response through what appears to be a mechanism of intracellular antigenic competition. Antigen presentation in this system is by host cells, as judged by lack of donor-specific restriction. Memory resides in both the CD45RA+ and CD45RA- compartments, although the majority of memory T(h) cells have the latter phenotype.