Positive and negative immunoregulation of normal and tumor-bearing mouse T cell blastogenesis

• Main Author: Connolly, Kevin Michael
• Other Authors: Microbiology
• Format: Others
• Language: en
• Published: Virginia Tech 2014
• Subjects: LD5655.V856 1979.C665; T cells
• Online Access: http://hdl.handle.net/10919/39002; http://scholar.lib.vt.edu/theses/available/etd-07282010-020423/

Using the mixed lymphocyte reaction (MLR) as a correlate of cell-mediated immunity, an examination was made of positive and negative blastogenic immunoregulation by syngeneic peritoneal macrophages (M_Φ) and splenic T cells from tumor-bearing mice (TBM). As analysis of T cell proliferative response progressed an intricate pattern of immunoregulatory checks and balances unfolded involving both M_Φ and TBM cells. In their capacity as regulators, M_Φ acted, not only to enhance MLR reactivity, but to inhibit it. Results indicated that: i) M_Φ regulation was a concentration dependent phenomena -- high concentrations of M_Φ (or their supernatants) inhibited MLR reactivity, while low doses enhanced MLR reactivity; ii) inhibition occurred via a non-toxic, heat stable, nondialyzable (and therefore non-thymidine) factor; iii) enhancement occurred via a heat labile nondialyzable factor. Since normal M_Φ possessed a factor which, in high concentrations, inhibited T cell blastogenesis, tests were run to determine if the MLR hyporeactivity of T cells from TBM could be attributed to a unique tumor-induced inhibitory M_Φ. Contrary to expectations, TBM M_Φ supernatants, when compared to their normal counterparts on a volume-to-volume basis. showed an increased (not decreased) ability to enhance MLR reactivity. In light of results showing TBM M_Φ enhancement of MLR reactivity, T cell hyporeactivity in TBM was explained after observation of the following dual regulatory mechanism of suppression: i) on a purely quantitative basis, the high in vivo concentration of M_Φ in spleens of TBM inhibits spleen cell response to alloantigen; ii) there also exists a population of mildly nylon wool adherent tumor-induced splenic T cells which elaborate a soluble factor capable of overriding any M_Φ enhancing effect. In their capacity as regulators, tumor-induced splenic T-cells act, both to enhance and inhibit MLR reactivity. Whereas M_Φ regulation is concentration dependent, in the case of the T cell regulator, regulation is based, not upon the relative concentration of the regulator cell, but upon the level of responder cell activity, i.e. M_Φ-depleted MLR cultures (showing minimal proliferation) were enhanced by regulator TEM T cell addition, while M_Φ augmented MLR cultures or PHA stimulated cultures (with a high rate of blastogenesis) were inhibited by the same concentration of TBM regulator cells. Centering around more stringent biophysical and biochemical characterization of M_Φ supernatants, the latest work has resulted in the biochemical separation of M_Φ supernatants into inhibitor and enhancing components. Using anion exchange chromotography and slab gel electrophoresis, inhibitor and enhancing factors have been separated by charge. Treatment of M_Φ with indomethacin did not abrogate release of inhibitor factor, suggesting that it was not prostaglandin. Enhancing factor, obtained from M_Φ sonicates as well as supernatants, could be distinguished from lymphocyte activating factor by its inability to induce a thymocyte PHA response. Thus, analysis of regulation in the cell-mediated immune system has resulted in the elucidation of a most elaborate scheme of immunoregulation involving both M_Φ and T cells. === Ph. D.