ANALYSIS OF ANTIGEN PRESENTATION USING HLA TRANSFECTANTS

In summary, the transfection of HLA class II sequences is proving a useful tool for various aspects of the analysis of antigen presentation. Such transfectants have been used in the generation of new polymorphic HLA mAbs and in mapping the specificities of existing mAbs. In terms of analysing the HLA restriction of particular T cell clones, transfectant APC are increasingly being used as a means of identifying the presenting class II molecule, a less equivocal approach than mAb blocking studies or presentation by B-LCL panels. Our studies with DR2-restricted clones showed that, as with other haplotypes which generate two DR products, one of the two expressed DRβ chains is functionally dominant. Once restricting molecules for interesting clones have been worked out, spe cific sites in the cDNA can be readily mutagenised to establish the areas of interaction between peptide, class II and TCR. On the more general question of APC function, transfected L cells are capable not only of presenting peptide antigens but also process complex antigens, suggesting that some of the degradative pathways necessary for processing are generally available in diverse cell types. The ability of transfectants to function as APC seems to extend, at least in some cases, to the presentation of allodeterminants. HLA class II transfected L cells which were poor at presenting either soluble antigen or allo-antigen to T cells owing to insufficient levels of class II expression could be made into potent APC by retransfection with ICAM-1, restoring the accessory molecule interaction between LFA-1 and ICAM-1. This approach is proving valuable in defining the role of such accessory molecules in antigen presentation. With the ability to generate powerful tools for the in vitro dissection of HLA function as well as the appearance of transgenic mice for in vivo studies, the coming years should yield exciting advances in understanding the complexities of antigen presentation in human immunity. © 1990 S. Karger AG.