Reactivity of a rabbit antiserum against highly purified HLA-DR antigens

Abstract

A rabbit antiserum has been raised against highly purified, detergent-solubilized HLA-DR antigens. Externally or internally labelled surface glycoproteins from B-lymphocytes, epidermis, macrophages, and B-lymphoma cell lines reacted with the antiserum which precipitated polypeptide chains with the molecular weights 28,000 and 34,000. Such polypeptide chains were not observed when the antiserum was reacted with T-lymphocytes, T-cell lymphoma lines, kidney, brain, thymus and spermatozoa. Fab-fragments of the antiserum completely abolished the cytotoxic action of HLA-DR allantisera but had no effect on the cytotoxicity mediated by HLA-A,B and C loci antisera. Moreover, the rabbit antiserum reacted with the same molecules as the HLA-DR alloantisera. Fab-fragments of the rabbit antiserum completely abolished the MLR response and from the kinetics of the inhibition it is concluded that the Fab-fragments may interfere primarily with the initial recognition phase of the MLR.