An IgG Anti‐IT Detected in a Caucasian American

An isoantibody was detected in the serum of a Caucasian with Hodgkin's disease. The antibody reacted strongly by the indirect antiglobulin test with all fetal cord cells but was negative or only weakly positive when tested with adult cells, including five examples of the rare adult i cells. Rhesus monkey and rabbit cells also failed to react. No autoagglutination was seen and the direct antiglobulin test was negative. The antibody sensitized cells optimally at 37 C, reacting with anti‐IgG but not anti‐IgM, anti‐IgA or anti‐complement antiglobulin reagents. It was not inhibited by human saliva, milk, or 2‐mercaptoethanol. The specificity met the criteria set for anti‐I T . It is unique among antibodies of this specificity since it is an IgG isoantibody, reacting optimally at 37 C by the indirect antiglobulin test, showing a marked difference in reaction between cord and adult cells and occurring in a Caucasian. This contrasts with the only other anti‐I T antibodies described in the literature which are all cold autoagglutinins occurring in isolated populations (Melanesians and Yanomama Indians of Venezuela), showing only marginal differences between adult and cord cells.