Cell-mediated immunity against Besnoitia and toxoplasma in specifically and cross-immunized hamsters and in cultures

The capacity of hamster peritoneal cell populations to control viability and growth of Besnoitia and Toxoplasma organisms was assessed in vivo and in vitro. Immunized hamsters reduced the homologous organisms 100- to 10,000-fold over a 5-day period, but the heterologous infection increased 100- to 1,000-fold in numbers, similar as in the nonimmune controls. Passively administered antibody was ineffective although lytic cofactors were supplied by hamsters. In cultures, peritoneal cells from Besnoitia-immune hamsters delayed the growth of homologous parasites to an average of 38.5 h per division; however, in Toxoplasma-immune and nonimmune cells, Besnoitia divided every 12.8 h. Specificity of immunity was pronounced against both infections. With cross-infections, Toxoplasma-immune cultures did not effectively delay Besnoitia growth; however, Besnoitia-immune cultures reduced Toxoplasma growth by one-half. Co-cultivation experiments demonstrated that specifically committed lymphocytes could instruct macrophages to reduce the homologous organism 10-fold, whereas heterologous organisms were reduced only 2-fold. Lymphocyte supernatants initiated hypersensitivity as indicated by macrophage activation and giant cell formation in culture. However, these supernatants did not transfer infection immunity. Lymphokines could account for the hypersensitivity phenomena, but cell-mediated infection immunity in this model required close lymphocyte-macrophage proximity. These studies indicate that a number of distinct processes including delayed hypersensitivity, macrophage activation, and specific cellular immunity are acting simultaneously during latent Besnoitia infection of hamsters. All three processes are mediated by lymphoid cells and appear to be specifically induced. Although activated macrophages develop some heightened nonspecific capabilities, these were several orders of magnitude below the specific effects.

Some aspects of intracellular parasitism

In intracellular parasitism the host cell is a true and hospitable host. The parasite does not have to break in the door. It has subtle ways of inducing the host to open the door and welcome it in. One of the exciting fields in the future of parasitology is to find out what these ways are and why they are sometimes so highly specific that the cell that invites one parasite in will not open the door to another closely related species. Once inside, the parasite not only exploits nutrients already available in the cell, and the cell's energy-yielding system, but it further induces the cell to assist actively in its nutrition. Like a bandit who has cajoled his way in, the parasite now forces his host to prepare a banquet for him. Finally it may destroy its host cell, as in most of the associations I have described herein, or it may stimulate its host cell to abnormal increase in size or to have an altered metabolism with the formation of new products. Or it may even contribute some positive benefit to the host cell or to the multicellular organism of which the cell is a part, so that the two kinds of organisms then live together in a state of mutualism or symbiosis (26).

Serum IgE levels in protozoal and helminthic infections

Serum IgE concentration is measured, according to the Rowe modification of the Mancini technique, in non-atopic patients suffering from various helminthic or protozoal infections. Our results indicate that the IgE level is often raised in parasitosis with prominent tissue phases and remains normal with helminths whose life is restricted to the lumen of the digestive tract. In addition, our observations show that, with helminthic or protozoal infestations, the serum IgE level tends to increase significantly and rapidly following a specific treatment of the parasitosis. Afterwards, the serum IgE level decreases slowly and may return to the normal in a few months. Thus, repetitive evaluations of serum IgE concentrations, before and after therapy, appear to be of a diagnostic value in the cases where a vague clinical picture is suggesting an helminthic parasitosis.

Absence of immunity between Trypanosoma musculi and intra-erythrocytic protozoa in mice

Mice which have recovered from, infections with Trypanosoma musculi exhibit no immunity to challenge with the malaria parasites, Plasmodium v. vinckei, P. v. chabaudi, P. b. berghei, P. b. yoelii or P. atheruri, the piroplasms Babesia rodhaini or B. microti or the dactylosomid Anihemosoma garnhami. Recovery from infections with any one of these parasites confers no immunity against T. musculi. These results indicate that heterologous immunity between intra-erythrocytic protozoa does not extend to trypanosomes.

Changes in macrophage metabolism in mice heavily infected with Hexamita muris

The rate of 3H-RNA synthesis is increased in macrophages cultured from mice with severe, and often fatal, infestation with the intestinal flagellate Hexamita muris. The response of the cultured macrophages to foreign antigen is also impaired at such times. The macrophages behave normally when the flagellate is present as a commensal.

The pathology of the heavily infested mice is described and the results are discussed with reference to present concepts of the role of the macrophage in immunity.

Plasma immunoglobulin concentrations in a West African (Gambian) community and in a group of healthy British adults

Plasma concentrations of IgG, IgA, IgM and IgD of 1123 members of a native West African (Gambian) community and of ninety-one British adults were measured using a single radial diffusion technique. The African plasmas showed changes of immunoglobulin concentration with age which were characteristic for each class.

Gambian children attained adult levels of IgG by about the 5th year of age. Mean IgG concentration in Gambian adults was approximately twice that of the British adults.

IgA was not detected in Gambian children in the first few days of life. British and Gambian adults showed a similar broad range of IgA concentrations, and in Gambians the range broadened progressively with increasing age.

IgM was detected in all Gambian sera, including that from the youngest children. Values rose rapidly during the first 3 months of life. In Gambian adults a broad range of values was found, with higher values becoming more frequent in the elderly. IgM levels in some Gambian sera were conspicuously increased compared with the British sera, but the anticipated increase of 19S proteins in the ultra-centrifuge was not found. High IgM levels were not associated with evidence of infection with Trypanosoma gambiense, nor were the findings typical of Walden-ström's macroglobulinaemia.

IgD was not detected in Gambian children less than 2 months of age, but a broad range of values was found in childhood and adolescence. In adults higher levels occurred less frequently and the distribution of levels was similar to that of the British population.

The significance of these findings is discussed.

Trends in research on the immunology of trypanosomiasis

It was thought timely, in view of the increasingly close association between immunology and parasitology, to attempt a synthesis of research on trypanosomiasis immunology-research which may be expected both to lead to the solution of practical problems in this disease and to provide models for the study of basic immunological problems.The author's discussion is based on four main applications of immunological knowledge: for diagnosis, for immunization of hosts, for explanation of pathological effects, and as a contribution to the understanding of cell function. Stress is laid on the importance of determining the range and extent of antigenic variation in trypanosome material, whether with a view to the development of reliable diagnostic tests (although quantitative estimation of IgM in serum and cerebrospinal fluid is a useful diagnostic tool circumventing the difficulties caused by antigenic variation during an infection) or for assessment of the possibility of developing antitrypanosomal vaccines. Emphasis is also placed, inter alia, on the need for standardization and determination of the purity of stabilate material exchanged between research laboratories.