Features of cells controlling H-2-restricted presentation of antigen to T helper cells in vivo.

Information was sought on the nature of cells presenting antigen (sheep red blood cells) in an H-2-restricted fashion to T helper cells in vivo. The approach used was to examine the capacity of F1 hybrid T cells to collaborate with parental strain B cells after prior positive selection of the T cells to antigen in irradiated parental strain mice in the presence of various sources of Thy 1-negative cells taken from F1 or parental strain mice. The results showed that H-2-restricted presentation of antigen to T cells is controlled by radioresistant, nylon-wool adherent. Thy 1-negative cells, which are enriched in spleen and peritoneal exudates, rare in lymph node cell suspensions, and undetectable in thoracic duct lymph; pretreatment in vitro with anti-Ia reagents directed either to I-A or I-E subregion determinants abolished antigen-presenting activity. These findings correlate closely with the known characteristics of cells that present antigen in vitro. Studies in which re-irradiated parent leads to F1 chimeras were used as hosts for positive selection suggested that nonhematopoietic cells do not play a discernible role in antigen presentation.