Toxoplasma gondii antigens recognized by sequential samples of serum obtained from congenitally infected infants.

The Sabin-Feldman dye test, the immunoglobulin M (IgM) immunosorbent agglutination assay, and the immunoblot technique were used to study the evolution of the antibody response to Toxoplasma gondii and to examine antigens of the organism recognized by antibodies in the sera of 12 congenitally infected infants and 7 mothers. In the sera of eight infants, a significant rise was noted in the dye test titers, while the serum of only one infant demonstrated a late increase in the IgM immunosorbent agglutination assay titer. In each infant and mother, antigens with approximate masses of 35,000 and 115,000 daltons were strongly recognized by IgG antibodies. An antigen(s) with an approximate mass of 4,000 daltons was recognized by IgM antibodies in the sera of each of the mothers but was recognized by antibodies in the sera of only two of the infants.