Immunity patterns during acute infection by Eimeria bovis.

Cellular and humoral responses were investigated following gavage inoculation of 6-wk-old bull calves with 35,000-40,000 oocysts of Eimeria bovis. At 3-4-day intervals for 40 days after inoculation (DAI), blood was taken and assessed for serum IgG against merozoites and sporozoites of E. bovis. Proliferative responses of peripheral blood lymphocytes were measured following stimulation with either concanavalin A (Con A) or a soluble antigen derived from E. bovis oocysts (EbAg). Serum IgG against merozoites and sporozoites reached a peak of activity between 10 and 20 DAI, coinciding with oocyst shedding on days 17 to 24. Serum antibody titers had dropped to base levels by 40 DAI, although anti-merozoite titers remained elevated for the duration of the study (i.e., from days 12 and 20 to day 40). Con A stimulation of lymphocytes was not affected by infection; there was no evidence of suppressed or augmented responsiveness. Lymphocyte responses to EbAg had reached a maximum by day 20 and remained elevated throughout the study. These results indicate (a) that sporozoites and merozoites share antigens recognized by serum IgG, (b) that there is no episode of marked immunosuppression during acute infection, and (c) that cellular immunity is probably more important in resistance against reinfection than humoral immunity.

Antigenemia in recently acquired acute toxoplasmosis.

An enzyme-linked immunosorbent assay (ELISA), designed to detect low concentrations of antigens of Toxoplasma gondii, was used to determine whether antigenemia is present in patients with recently acquired acute toxoplasmosis. The ELISA detected antigenemia in 15 (65.2%) of 23 sera from 22 patients with recently acquired acute toxoplasmosis. Antigenemia was not detected in sera from 28 normal (seronegative for antibodies to Toxoplasma) individuals or from 55 individuals chronically infected with T. gondii. Sera from 13 individuals who were not infected with Toxoplasma but who had circulating rheumatoid factor were positive with normal and Toxoplasma-infected rabbit IgG but not with the F(ab)2 fractions. Sera from each of the 15 patients in the acute phase of infection did react with the F(ab)2 fraction of Toxoplasma-infected rabbit IgG but not with the F(ab)2 fraction of normal rabbit IgG. In preliminary studies, toxoplasma antigens were also detected in amniotic fluid and cerebrospinal fluid of newborns with congenital toxoplasmosis.

Antigenic streptococcal components in acute glomerulonephritis.

Fluorescein-labeled immunoglobulin G fractions from serums of patients with acute glomerulonephritis and from many normal serums stained the glomerular basement membrane and mesangium of renal tissue from patients with early acute glomerulonephritis; these serums did not stain the corresponding tissues from patients with any other kidney disease. Previous absorption of the serum fraction with frozen and thawed nephritogenic beta hemolytic streptococci abolished all staining. Other bacteria studied did not abolish the staining. Only the plasma membrane of the streptococcus absorbed the immunoglobulin G fraction; such absorption eliminated staining. Fluorescein-labeled antiserums against streptococcal plasma membrane had staining properties similar to patients' serums.