Identification of three antigens in human brain associated with similar antigens on human leukaemic cells.

Monoclonal antibodies prepared against a non-T and non-B acute-lymphocytic-leukaemia cell line were tested for reactivity against human brain tissue. Several of the monoclonal antibodies were found to react specifically with brain fractions. Three antigens, 44H4, 44D7 and 44D10, were identified in white matter. Although 44D10 was absent from grey matter, the levels of 44H4 and 44D7 antigens present in grey matter were 2- and 4-fold higher respectively than in white matter. Fractionation of white matter indicated that all three antigens were absent from the multilamellar compact myelin, but associated with a membrane fraction of higher density. All three antigens, which required detergent for solubilization from the membranes, were purified by affinity to monoclonal antibodies and/or were analysed by immunoblotting. The 44H4 and 44D10 antigens were single polypeptide chains with Mr 94000 and 80000 respectively when resolved by sodium dodecyl sulphate/polyacrylamide-gel electrophoresis. Monoclonal antibody 44D7 reacted with a complex of a Mr greater than 120000 under non-reducing conditions in the presence of sodium dodecyl sulphate. This complex dissociated on reduction into four bands with Mr values of 80000, 57000, 47000 and 41000. The brain antigens are present on proteins similar to, or identical with, those isolated from acute-lymphocytic-leukaemia cells.