ANALYSIS OF FUNCTION OF A HUMAN ANTIGEN-PRESENTING CELL BY XENOGENEICINTERACTION WITH MOUSE T-CELLS

A human B cell line, ARH, was transfected with a murine major histocom patibility complex class II gene (I-A(k)). One of the transfectants, A RH5.5, which strongly expresses I-A(k) molecules was found to be capab le of presenting soluble antigens to I-A(k) restricted, antigen-specif ic murine helper T cell (Th) clones. When ARH5.5 was treated with eith er chloroquine or paraformaldehyde prior to the antigen pulse, it fail ed to present a protein antigen, ovalbumin, but retained the ability t o present a peptide, indicating that the presentation was dependent on processing. The xenogeneic interaction of co-stimulatory molecules on the human antigen presenting cell (APC) and the murine Th cell was as sessed by using antibodies against adhesion molecules. We found that t he xenogeneic interaction of LFA-1/ICAM-1 acted as a strong co-stimula tor of the antigen presentation by ARH5.5, while that of CD2/LFA-3 had only little stimulatory effect. These results suggest that the intera ction between some of the adhesion molecules on APC and Th can cross t he species barrier. The experimental system presented here is simple a nd useful for analyzing human APC function, separately from T cell fun ction, especially when the dysfunction of APC associated with viral in fection with human tropism is considered.