Reactivity of a Rabbit Antiserum against Highly Purified HLA‐DR Antigens

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Abstract
A rabbit antiserum was raised against highly purified, detergent-solubilized HLA-DR antigens. Externally or internally labeled surface glycoproteins from B[bone marrow-derived]-lymphocytes, epidermis, macrophages and B lymphoma cell lines reacted with the antiserum which precipitated polypeptide chains with MW 28,000 and 34,000. Such polypeptide chains were not observed when the antiserum was reacted with T[thymus-derived]-lymphocytes. T cell lymphoma lines, kidney, brain, thymus and spermatozoa. Fab-fragments of the antiserum completely abolished the cytotoxic action of HLA-DR alloantisera but had no effect on the cytotoxicity mediated by HLA-A, B and C loci antisera. The rabbit antiserum reacted with the same molecules as the HLA-DR alloantisera. Fab-fragments of the rabbit antiserum completely abolished the MLR [mixed lymphocyte reaction] 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.