Soluble HL‐A antigens in serum. I. Isolation and Purification

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Abstract
A new method was developed which utilizes fractional salting out, gel filtration, ion exchange chromatography and polyacrylamide gel electrophoresis for the isolation and purification of soluble HL-A antigens from serum. The method produced purified antigens possessing HL-A 5,9 specificities with yield up to 60 % of that detected in the original serum. Up to 150-fold increase in specific HL-A antigenic activity above that in the starting material could be achieved as measured by the ability of the purified antigens to specifically inhibit the cytotoxic activity of HL-A alloantisera against selected target cells. Electrophoretically purified HL-A antigens with different specificities appear to have a similar molecular size, i.e. 33 000, but differ in their electric charge properties. β2-microglobulin (β2m) seems to be noncovalently associated with HL-A antigens present in serum, but during purification β2m is progressively lost until at the final purification by polyacrylamide gel electrophoresis, the material is completely devoid of β2m.