Development of Gm Antibodies Following Injection of Anti‐Rh Gamma Globulin

The incidence of antibody formation to Gm(1), Gm(5) or Gm(4) antigens in Rh‐negative mothers was determined following injections of pooled anti‐Rh γ globulin for the prevention of Rh isoimmunization. A 4.1 per cent frequency of Gm antibodies following a first injection in 316 mothers was found, compared to a 1.0 per cent frequency in a control noninjected population. Two injection volumes (either 4.5 ml or 1.0 ml) were administered to mothers in the first injection group. A significant number of Gm antibodies developed in mothers given the 4.5 ml injection, but not in those receiving 1.0 ml. In small second and third injected groups, given 1.0 ml of γ globulin, no increase in incidence of Gm antibody formation occurred. The γ globulins in the sera of eight mothers were separated into 19S and 7S components. Gm antibody activity was found in the 19S fractions of all specimens and in the 7S fraction of one. Positive latex fixation reactions following injection were detected in the sera of two mothers who developed Gm antibodies. The potential hazards of Gm antibodies are discussed, but the data suggest that these antibodies pose little immunologic threat to mother or child. Gm factors in humans are a group of genetically determined antigens located on the heavy chains of γG globulins. Development of anti‐Gm antibodies may result from the administration of blood or blood products containing γ globulins. 1 7,15 The use of anti‐Rh containing γ globulin in pregnant Rh‐negative women, for the prevention of primary maternal Rh hemolytic disease immunization, 14 raises the question of whether anti‐Gm sensitization occurs in these mothers and, if so, what if any consequences result. This report adds to presently available data regarding the formation of Gm antibodies following injections of anti‐Rh‐containing γ globulin, 2,3,18 by detailing observations made on 387 Rh‐negative mothers administered one or more injections.