[Impairment of humoral immunity in aging].

1) Aging is associated with a hypergammaglobulinemia consistng of an increase in the serum IgG and IgA, plus a reduction in the IgM. This is associated with an increase of the B lymphocyte circulating pool, and an increase of the ratio IgG-B cells; 2) There is a reduction of the serum concentration of natural isoagglutinins. 3) The secondary IgG response against diphteria toxin (DT) is similar in 15 young and 15 old subjects. 4) There is a reduction of the IgE response against DT in old subjects.