The induction of transmission-blocking immunity as a potential tool in malaria control was first reported in 1976 by Gwadz (1) and Carter and Chen (2) for the avian malaria parasite Plasmodium gallinaceum. Subsequent reports confirmed that the immunogens were present on the surface of both male and female gametes (3, 4). Similar results were reported for a simian malaria parasite, P.knowlesi (5), and the murine P. yoelii (6). This work was extended to the midgut stages of P. gaUinaceum by Kaushal and coworkers (7-10). Since the introduction of the in vitro culture for P. falciparum (I 1), good progress has been made ill biochemistry and molecular biology of the asexual parasites. The sexual stages, however, demanded special culture conditions. The availability of gametocytes and gametes as well as the establishment of routine in vitro infection of mosquitoes (12) were basic for further studies on this human malarial parasite. In 1983 Rener et al. (13) demonstrated that monoclonal antibodies (mAb) 1 against P.falciparum gametes could interfere with the transmission of this parasite to mosquitoes.We here present results of experiments regarding the nature of antigens on the sexual stages of P. falciparum, and their involvement in the blocking of transmission by monoclonal and polyclonal antibodies. These antigens are sequentially expressed in gametocytes, on the surface of gametes, or on ookinetes.

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More than 500 specimens of lung tissue were examined for Pneumocystis. Of the 38 infections detected, most were in immunodeficient patients. Samples of serum from approximately 600 healthy normal subjects and 117 children with acute lymphatic leukemia were examined by an indirect fluorescent antibody test. The age-related data from the normal children suggested that nearly 100% of children are infected with Pneumocystis during the first two years of life. Groups of patients with leukemia who had symptoms of pneumocystis pneumonia had significantly higher titers of IgG antibody than groups of patients with leukemia who did not have clinical symptoms and normal subjects. Nevertheless, the diagnostic value of the indirect fluorescent antibody test is limited, but serologic follow-up study can be useful. Groups of children with leukemia had lower mean titers of IgM antibody regardless of their clinical condition.

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