B6D2 F1 Research Articles

Mechanism of cellular suppression induced by oral tilorone treatment of mice.

Specific-pathogen-free B6D2 F1 hybrid mice were treated orally with tilorone hydrochloride (100 mg/kg of body weight per day) and infected with sublethal doses of Listeria monocytogenes, Salmonella enteritidis, Mycobacterium bovis (BCG Pasteur), or M. tuberculosis Erdman. Daily tilorone treatment inhibited the cell-mediated response to all of the intracellular parasites, and most of the mice succumbed to the challenge. Tilorone suppressed delayed hypersensitivity responses to the microbial sensitins as well as to sheep erythrocytes. However, humoral responses (immediate hypersensitivity reactions) were stimulated. The types of growth curves obtained in the tilorone-treated mice were quite different from those observed in T-cell-depleted mice and tended to resemble those seen in sublethally irradiated (400 rads) animals. Leukocyte counts were depressed 10-fold by daily tilorone treatment. Both monocyte and granulocyte (but not large-lymphocyte) counts were depressed. There was an initial drop in small-lymphocyte counts with a later recovery phase. Tilorone treatment reduced the granulomatous response within the Salmonella-infected liver, suggesting that the drug interferes with the mobilization of the mononuclear defenses within the normal host.

Further Characterization of Thymic Suppressor Cells and a Factor That Suppress the Generation of Cells Cytotoxic for a Syngeneic Tumor in DBA/2 Mice

Antigen-specific suppressor cells and suppressive extracts obtained from the thymuses of DBA/2 mice bearing small syngeneic P815 mastocytomas were compared for their immunogenetic properties and requirements. The assay for specific suppression involved the ability of either cells or extracts to inhibit the primary in vitro cytotoxic response of normal DBA/2 splenocytes to mitomycin-treated P815 cells. It was shown that pretreatment of suooressor cell populations with anti-Iad antiserum plus rabbit complement removed the suppressive activity. Similarly, absorption of the suppressor factor with anti-Iad antiserum removed the suppressive properties of the material. It was found that the suppressor cells, generated in DBA/2 tumor bearers, were capable of specifically suppressing the anti-P815 response of B6D2 F1 radiation chimeras possessing lymphoid cells of the H-2b or H-2t2 haplotype equally as well as they could suppress the response of H-2d-bearing effector cells. This indicates that the suppressor cells are not H-2 restricted with respect to K or D markers on the responder cells in this system.