Cellular and genetic control of antibody responses. VIII. MHC restricted recognition of accessory cells, not B cells, by parent-specific subpopulations of normal F1 T helper cells.

Normal F1 helper T cell populations were analyzed under conditions in which the number of T cells was strictly limiting so that anti-hapten PFC responses to TNP-KLH increased linearly with increasing numbers of T cells. The slope of the response line is a measure of the helper activity of the added T cell population and reflects the number of helper T cells activated. In this way, the recognition and activation requirements of normal F1 helper T cell subpopulations were analyzed. It was determined that the F1 helper T cells specific for recognizing antigen in the context of the MHC determinants of only one parent specifically recognized those determinants expressed on accessory cells, but not on B cells. Indeed, each parent-specific F1 T cell subpopulation was only triggered by one parent's accessory cells; but once triggered, each parent-specific F1 T cell subpopulation was capable of activating either parent's B cells.