Immunosuppressive alpha globulin from bovine thymus and serum: mode of action upon afferent and efferent arcs of the mouse immune response

Anti-immunoglobulin-induced proliferative response of rabbit lymphocytes in a serum-free medium

The aim of this study was to determine if rabbit lymphocytes were activated with a specific ligand, anti-immunoglobulin (anti-Ig) in a well-defined serum-free medium. A modified medium, composed of Neuman-Tytell (NT) basal medium supplemented with BSA, transferrin (Tf), and fatty acids (FA), was found to support a vigorous anti-Ig-induced proliferative response of rabbit lymphocytes. The optimal concentrations of BSA, Tf and FA supplements were determined for the mitogen-induced response. The mitogenesis was enhanced by addition of 2-mercaptoethanol. The proliferation could be maintained for 10 days provided cells received fresh medium and mitogen on day 5. The presence of anti-Ig throughout the culture period is required for this extended proliferation. The response did not require the Fc portion of the anti-Ig and was blocked by soluble rabbit F(ab')2 fragments. The anti-Ig-activated blasts lacked a T cell surface marker and about half of them re-expressed sIg when anti-Ig was washed out (assayed 24 h later). The viability of the mitogen-induced cells on day 5 was above 55%, whereas the viability of the cells without mitogen was 36%. The supplemented NT medium could also support Con A-induced mitogenesis of rabbit lymphocytes. Additionally, Con A- and LPS-stimulated murine lymphocytes showed considerable proliferation for up to 5 days in the supplemented NT medium.

Tumor associated immunosuppression in mice bearing anaplastic carcinoma

The effect of anaplastic carcinoma (15091A) and fibroblast cell culture supernates was examined in conjunction with Concanavalin A (Con A) on the splenic lymphocyte transformation of syngeneic A/J mice. Though both the tumor and normal cell culture supernates caused a dose-dependent suppression of the in vitro DNA synthesis of lymphocytes, larger depressive effects were observed with the former. Similar results were observed with supernates collected from tumor cell and fibroblast cultures in 10% heat inactivated fetal calf serum or serum-free media. The results of these experiments indicate that the depressed immunological reactivity observed in animals and human with cancer may be attributed to enhanced release of immunosuppressive factor(s) by malignant tissue into the body fluids of hosts.

Antigen-specific suppressor cells and suppressor factors in human filariasis with Brugia malayi

We investigated the mechanisms of specific immune unresponsiveness to microfilarial antigens. The blood of patients with obvious Brugia malayi infections contains an adherent cell type that specifically suppresses reactions to microfilarial antigens but not to other antigens. In the absence of continued stimulation by parasite antigens, this suppressor cell loses its functional activity after overnight culture in vitro. Furthermore, serums from patients with and without microfilaremia contain factors that also suppress reactions to filarial antigens in vitro. These results suggest that immune unresponsiveness in human beings with patent filarial infections is due to active suppression of immune responses directed against the parasite and not to an intrinsic inability of infected patients to react to parasite antigens.

Some endocrine aspects of the thymus gland

In studies of the mouse thymus, lymphocyte mitoses are seen to be most frequent in the thymus cortex. There is evidence from thymic grafts that a hypothetical factor, thymopoietin, may stimulate mitosis of thymic lymphocytes. It is a factor which is postulated to act in conjunction with the PAS-positive mesenchymal reticular cells and epithelial reticular cells of the cortex. The thymus medulla is necessary for the integrity of thymic grafts, and may also elaborate a secretion for maintaining the cellular functions of the gland. Thymectomy has been used as a gauge for judging normal thymic function and results, in the mouse, in lymphopenia, degeneration of spleen and lymph nodes, delayed rejection of skin allografts, reduced ability of spleen cells to mount the graft versus host reaction, and reduced primary immune response to certain antigens. Correction of these deficiencies offers a means of evaluating various thymic extracts and grafts. Lymphocytosis-stimulating hormone (LSH) is known to maintain the peripheral lymphoid organs and cause lymphocytosis in the thymectomized animal. Diffusion chamber studies of thymic grafts also show restored lymphoid tissue by a cell-free factor (CIF). These two factors may be the same and probably represent the basis of the highly purified lymphocyte-stimulating proteins, LSHr and LSHh, which restore the L/P ratio in thymectomized animals and may stimulate lymphopoiesis in spleen and lymph nodes. LSHr, unlike LSHh, increases the total lymphocyte count. LSHr has been found to increase the humoral antibody response in neonatal mice both by the PFC technique and by direct hemolysis of sheep erythrocytes. Homeostatic thymic hormone (HTH) is a thymic extract of small molecular weight and contains nucleic acid. In the thymectomized guinea pig it has been found to maintain normal levels of lymphocytes in the blood, spleen and lymph nodes, to restore antibody titers to typhoid H antigen and to restore the toxic allergic reaction. Thymic humoral factor (THF) is of smaller molecular weight (less than 1,000) and probably is not a protein. It also enhances lymphoid proliferation in neonatally thymectomized mice. There is evidence that THF participates in humoral antibody formation because it stimulates PFC formation from neonatally thymectomized mice after inoculation with sheep erythrocytes. Its effects on cell-mediated immunity are seen from findings that injection of THF restores the ability of thymectomized mice to reject skin allografts. THF enables spleen cells from thymectomized or neonatal animals to mount the graft versus host reaction, and causes maturation of bone marrow cells and spleen or lymph node cells so that they can participate in the graft versus host reaction. It has been reported to stimulate lymphocytes to kill isogeneic tumor cells in vitro. Thymosin is protein extracted from the thymus. It has been found to alleviate leukopenia slightly and provide some improvement in lymphoid histology in thymectomized mice...