Age-dependent changes of isotype and idiotype expression in the antibody response to the phosphorylcholine hapten in BALB/c mice

The distribution of antibodies among different isotypes in an immune response to a given antigen reflects the immunoregulatory linkage of T and B cell compartments, the genetic background of an individual and the functional state of its immune system. In addition, idiotypes are markers for the clonal origin of antibodies and their genetic relationship. Therefore, we have analyzed the isotype patterns and development of the major idiotype (T15) in BALB/c mice of different ages, immunized with a T-cell-dependent phosphorylcholine conjugate. The response was dominated by mu, gamma 3 and gamma 1 isotypes. The proportion of these antibodies changed in the progress of immunization but not with age in the primary response. An age-dependent change of the isotype distribution was observed only in the memory response. The T15 idiotype was dominantly expressed in the primary response and decreased in the memory response by 80-95% independently of the age of the mice. The results demonstrate that 2 populations of anti-phosphorylcholine antibodies which both prefer particular isotypes are expressed according to the functional state of the T and B cell compartments with age.