The effects of cortisone on immunity during chronic rodent malaria

Androgen control of immunocompetence in the male house finch, Carpodacus mexicanus Müller

The immunocompetence handicap (ICH) hypothesis predicts that elevated levels of the gonadal androgen testosterone (T) entail obligatory costs, such as immunosuppression, but evidence supporting this immunosuppressive influence is equivocal. To investigate this question, adult males house finches, Carpodacus mexicanus, were exposed to short days and chronically treated with T-filled (T males; N=10) or empty (C males; N=10) Silastic capsules. Testosterone administration increased plasma T levels and the size of the cloacal protuberance, an androgen-dependent secondary sexual characteristic. To study humoral immunity, finches received injections of sheep red blood cells (SRBC) and we measured circulating concentrations of antibodies to these cells with a hemagglutination test. All males produced antibodies following four SRBC injections at weekly intervals. Antibody titers in T and C males did not differ 5 days after the fourth injection, but were 59% lower in T than C males 2 weeks later. To study cell-mediated immunity, we measured the local inflammatory response to an injection of phytohemaglutinin (PHA). This response in T and C males was similar 1 day after PHA injection, but was 58% less in T than C males 2 days following the injection. Thus, T and C males mounted similar humoral and cell-mediated immune responses, but T treatment compromised maintenance of these responses. The results, demonstrating immunosuppressive effects of elevated T, are consistent with the ICH hypothesis.

[Malaria tropica in HIV infection]

This is a case report of a 24 year-old woman who is HIV-infected since three years (stage III B, CDC). She developed malaria tropica during her touristic stay in the Cameroons, Africa. No clinical complications were detectable even though she had a high parasitemia of 18% blood cells infected with Plasmodium falciparum. After quinine therapy defervescence occurred and blood smears were continuously free of malaria parasites. P. falciparum infection may increase HIV-related immunosuppression which favours the earlier occurrence of AIDS indicative opportunistic infections. Malaria in combination with HIV-infection can lead to a higher parasitemia; this does not necessarily lead to a higher rate of complications.

Presence and characterization of lymphocytotoxins in acute and chronic Plasmodium berghei malaria

The role of lymphocytotoxic antibodies in elimination of lymphocytes and characterization of these antibodies during Plasmodium berghei infection was examined in BALB/c mice. When assayed at 15 degrees, an increase in lymphocytotoxic levels above base line values was detected in acute infection when parasitaemia exceeded 10%. There was an increase in lymphocytotoxins with increase in parasitaemia to a plateau beyond 25% parasitaemia. When assayed at 37 degrees, lymphocytotoxic activity during acute infection was lower than at 15 degrees but the increase detected was significant. During chronic infection there was a lower increase in the activity detected at 15 degrees and no significant increase in activity assayed at 37 degrees (P greater than 0.05). In addition, peripheral blood lymphocyte counts also dropped during acute infection while there was little change in lymphocyte numbers in the chronic infection group. The lymphocytotoxic antibodies present in sera of infected mice were predominantly of IgM class during acute infection and IgM or IgG class during chronic infection. The relevance of these observations to plasmodium infection is discussed.