Soluble HLA antigens not detected in human immunoglobulin preparations

Immunoglobulin concentrates prepared from subjects of known HLA specificity were assayed for the presence of soluble HLA antigens by the inhibition of cytotoxic HLA alloantisera using a microabsorption procedure. The immunoglobulin preparations inhibited alloantisera of all specificities tested, regardless of the HLA type of the immunoglobulin donor, indicating that the observed inhibition was non-specific. Addition of extra complement reduced the inhibitory effects of the immunoglobulin concentrates. It is concluded that the inhibition of HLA alloantisera demonstrated by this technique is due to the anticomplementary activity of the immunoglobulin preparations, rather than their content of specific soluble HLA antigens.