Metabolically dependent and independent cell surface antigens

In contrast to metabolically dependent tissue-specific cell surface antigens (MDA) which are available for reactions with antibodies only on surfaces of metabolically active cells, the availability of the universally distributed blood group A or Forssman-type antigens on cell surfaces was found to be independent of the metabolic activity of cultured cells. In case of the MDA, cytotoxic reactions were induced by antibodies alone, resulting in a disorganization of the cellular sheet without a significant release of radioactive label. Radioactive release in this cytotoxic reaction was increased by the addition of complement without additionally affecting the degree of cell sheet disorganization. In case of Forssman and blood group A antigens, such morphologically demonstrable cytotoxicity required complement, and the resulting pathology was always accompanied by extensive release of cellular contents. The ability of anti-MDA antibodies to induce cytotoxic reactions in the absence of complement may be related to a vital role of MDA in cellular function.