IgA as a Blocking Factor in Human Malignant Melanoma

Abstract

Immunoglobulin A (IgA), isolated from the serum of patients with malignant melanoma, was found capable of abrogating the cytotoxic effect of sensitized lymphocytes on human melanoma target cells in vitro. IgG and IgM from melanoma serum, as well as IgA, IgG, and IgM from normal serum, did not have this ability. Blocking activity could be removed from melanoma serum or IgA fractions by absorption with melanoma tumor cells or antihuman IgA antiserum.