Neonatal injection of mice with rabbit anti-µ antiserum has been shown to produce complete loss of direct and indirect plaque-forming responses to sheep erythrocytes as well as loss of serum IgM and severe depressions of all other serum immunoglobulins. Similar injection of anti-γ1γ2 or anti-γ1 antibodies effects a loss of the indirect response but induces relatively minor alterations in serum Ig levels. Delaying initiation of anti-µ treatment until young adulthood results in a somewhat diminished effect on plaque-forming responses and serum Ig levels but triggers the release of high serum levels of an aberrant µ-bearing protein.
Anti-µ suppression of genetically thymusless mice indicates that at least part of the target cells for suppression are bone marrow derived. A working hypothesis for the maturation of humoral antibody-producing cell lines as it relates to these data is discussed.