I region-restricted antigen presentation by B cell-B lymphoma hybridomas.

The activation of T lymphocytes for many responses requires interaction with specialized antigen presenting cells (APC) which express I region associated (Ia) antigens. Cells of the monocyte-macrophage lineage and the recently described dendritic cell have been shown to be effective APC. Antigen-specific T cells appear to recognize a complex of antigen and Ia molecules on the surface of the APC and such joint recognition is the basis of the restriction of T-cell activation due to the major histocompatibility complex. The Ia molecules appear to be Ir gene products. However the biochemical nature of antigen presentation has been difficult to approach largely because of problems in obtaining sufficient numbers of highly purified APC. Although several Ia antigen-positive B lymphoma cell lines, which have proved very effective APC, have been recently described, they have all been of the same H-2d haplotype. We report here on hybridomas produced by fusion of normal C57BL/6 (B6) B cells (H-2b) to a hypoxanthine guanosine phosphoribosyl transferase (HGPRT) deficient variant of one of these lymphoma cell lines. The hybridomas appear to express functional Ia molecules of both parental cell haplotypes. Such cloned somatic cell hybrids should prove useful in studying the properties of Ir genes and Ia molecules in antigen presentation.