Positive direct antiglobulin test in normal individuals. II

Investigations into the IgG sub-types and number of molecules of IgG present on the red cells of 22 apparently normal healthy blood donors with positive direct antiglobulin tests are described. In all cases, the sub-type was IgG1 or IgG4, and none had more than 1000 mol of IgG per red cell. It is suggested that sequestration of IgG-coated cells only occurs when the number of IgG1 mol per cell reaches a certain level.