Role of the Thymus in Immune Reactions in Rats

Abstract

In the preceding papers (2-4) it has been shown that, in rats thymectomized early in life, there is a partial or complete suppression of immune phenomena of the type attributed to delayed hypersensitivity, specifically of skin sensitization to tuberculin or to purified protein (bovine serum albumin), experimental allergic encephalomyelitis, and skin homograft rejection. Evidence is presented that humoral antibody formation may be diminished as well. The present paper deals with histologic changes found in the lymphoid tissues of the animals employed in these studies. The principal finding is an almost complete absence of small lymphocytes from their usual position in the spleen and lymph nodes. Methods and MaterialsThe material of the present study consisted of hematoxylin-and eosin-stained paraffin sections of various lymphoid tissues removed at autopsy from animals described in the preceding papers. Selected sections were also stained for reticulln. The animals were classified on the basis of the amount of residual thymus ("thymectomized" means no thymus or less than 100 mg residual thymus). In the bovine serum albumin (BSA) and experimental allergic encephalomyefifis (EAE) experiments, the thymectomized animals were further divided into those which reactcd, i.e. developed appreciable Arthus or delayed reactivity to BSA or developed EAE, and those which did not. In the tables and graphs the word "reacted" is employed to designate the former group.For the purposes of the present study, sections were examined of the liver, spleen, and various lymph nodes and, in occasional animals, the gastrointestinal tract (multiple levels) and femoral marrow. In animals which received adjuvant in the left hind foot-pad, with or

The Proliferative and Anamnestic Antibody Response of Rabbit Lymphoid Cells in Vitro

“…The time agrees much better with the peak of proliferation in germinal centers, as was also noted in previous studies on the spleen (3). This does not suggest a relationship to delayed type sensitivity, since germinal centers are thymus-independent (25,26), and are much more dearly related to the humoral antibody response (27,28) particularly of the 7S anarnnestic type (1, 29,30). The other possible explanation is that the early proliferative response indeed occurs in cells carrying immunological memory for antibody production, but that the majority of these cells are still immature.…”

Anatomical Distribution of T and B Lymphocytes in the Rat

“…1, 8, and 10, respectively; center well, normal rat serum. There is complete fusion of the lines formed by ALSo, 1,8, and 10; and partial fusion of the lines formed by ALSB 1 and anti-Ig serum, and by ALSB 8 and anti-Ig serum.…”

“…Antisera absorbed in this manner have binding properties comparable to those prepared by the more rigorous methods employed in this investigation. DISCUSSION A congeries of evidence from studies in the chicken (19,20), mouse (21-23), rat (1)(2)(3)(4)24), and other mammalian species including man (25) has established the existence of at least two developmentally and functionally distinct populations of lymphocytes. T lymphocytes are produced under the influence of the thymus, whereas B lymphocytes arise from stem cells in the bone marrow and are formed in both normal and thymectomized subjects.…”

“…Thus, approximately 99 % of thymocytes, 90 % of TDL, and progressively smaller portions of lymphocytes obtained from lymph nodes, blood, spleen, and bone marrow were identified as being T cells in the rat. In frozen sections of lymph node and spleen, T and B cells were located in the thymus-dependent and thymus-independent regions described previously (1,2). However, unlike the results of Gutman and Weissman (42) who used anti-Thy-1 and anti-Ig sera as markers for T and B lymphocytes in the mouse, we are unable to detect the presence of small numbers of T cells in germinal centers or the presence of Ig molecules on the surface of germinal center lymphocytes.…”

Thymectomy and asbestos-induced mesotheliomas in rats

“…For this reason, and the fact that thymectomy markedly reduced the number of their tumourbearing animals, it was considered that a different immunological mechanism might be involved. The carcinogenicity factor in thymectomized rats might bave been greater had this group of rats lived longer, as immune competence (Waksman et al, 1962) falls off with age in thymectomized rats. Wagner et al (in preparation) found that only carrageenan (an agent cytotoxic for macrophages) among a number of substances, increased the mesothelioma rate.…”