Migratory patterns of B lymphocytes. I. Fate of cells from central and peripheral lymphoid organs in the rabbit and its selective alteration by anti-immunoglobulin

Generating the antibody repertoire in rabbit

We describe a model for B cell development and generation of the antibody repertoire in rabbits. In this model, B cells develop early in ontogeny, migrate to GALT, and undergo the first round of diversification by a somatic gene conversion-like process and by somatic mutation. We designate the repertoire developed by this mechanism as the primary antibody repertoire and it is this repertoire that makes the rabbit immunocompetent. We invoke GALT as the site for development of the primary repertoire because (1) surgical removal of GALT from neonatal rabbits results in highly immunocompromised animals, (2) in germfree rabbits essentially no lymphoid development occurs in GALT and the rabbits are immunoincompetent, and (3) the follicular development of rabbit GALT is highly similar to that of the chicken bursa, the site in which the primary antibody repertoire develops by somatic gene conversion in chicken. We suggest that once the primary antibody repertoire is formed, it is maintained by self-renewing CD5+ B cells and is expanded to a secondary antibody repertoire after the B cells encounter antigen.

Lymphocyte homing

The phenomenon of "homing" is discussed with respect to patterns of lymphocyte circulation and the molecules on the surface of both endothelium and lymphocytes that mediate this process. In addition, the data are analysed in the context of a model for lymphocyte homing.

Control of IgE responses

Peyer's patches (PP) in germ-free rats (GF) and in the hyper-IgE syndrome patient (HIES) differ from their conventional rat (C) and healthy human (HH) counterparts in that GF rats contained fewer (two-fold) PP and none was detected in HIES. Existing PP in GF rats had reduced cellularity (three-fold) and different B and T cell subsets: high numbers of IgE-bearing (sIgE+) B cells (approximately 15% of total cells), one-half of which also expressed sIgA, were present in GF rat PP while none was detected in C rat PP (less than 1%). GF rat PP also contained elevated numbers of sIgA+ cells and decreased sIgM+ cells, with elevated numbers of sThy 1+ RT 7.1+ Ig- T cells (suppressor phenotype) and reduced sThy 1- RT 7.1+ Ig- T cells (helper phenotype). The cellular composition of GF rat PP was converted to that resembling a C rat within 18 hr after (a) use of standard (unautoclaved) chow; (b) feeding with certain bacteria or "working" bacterial cell wall components (BCWC) and synthetic derivatives, murein, MTP-PE, and norMDP, but not with LPS, core lipid A, or lipoprotein; BCWC had no effect if injected intravenously; or (c) thymectomy. Each procedure resulted in (i) elimination of sIgE+ B cells and normalization of the other isotypes, and (ii) loss of T suppressor cells and normalization of T helper cells. After treatments, no sIgE+ cells were detected in bone marrow (BM), thymus, other lymphoid organs, or blood. PP were not detected in HIES, although they were present in HH (approximately 10/individual). P blood contained two distinct sIgE+ B cell subpopulations, the apparent source of which was mesenteric lymph node (MLN), the only organ in which high numbers of these cells (35%) (five nodes examined) were detected; far fewer IgE+ cells were found in spleen (less than 5%), and none was detected in BM, thymus, other LN, or appendix, which was virtually acellular. Virtually no IgE secreting plasma cells were detected in MLN, spleen, appendix, other lymphoid organs, or in gut lamina propria. IgE+ B cells in MLN were not detected in follicles (classical B cell areas); instead, they were found in high numbers in the thymus-dependent area and in medulla. Most follicles (greater than 98%) in MLN and spleen contained intercellular IgE complexed to bacterial antigen and/or CD23 (IgE-binding factor? antigen?), but contained no germinal centers.(ABSTRACT TRUNCATED AT 400 WORDS)

Staphylococcal protein A bound to Sepharose 4B is mitogenic for T cells but not B cells from rabbit tissues

The mitogenicity of protein A from Staphylococcus aureus bound to Sepharose 4B (SpA-S) was tested against mononuclear cells from normal rabbit spleens and Peyer's patches after using Sephadex G-10 adherence chromatography to deplete macrophages and Sephadex G-200 anti-rabbit F(ab')2 immunoabsorbent columns to obtain B-enriched lymphocytes. Macrophage-depleted unseparated lymphocytes and the B-cell-depleted (T-cell-enriched) fractions from both tissues consistently showed good mitogenic responses to SpA-S. In contrast, the B-cell-enriched populations from either tissue did not respond to SpA-S. Supplementary experiments employing glass adherence and T-cell autorosetting did not support the possibility that the more efficient immunoabsorbent method of B-cell isolation had in some way caused the unresponsiveness to SpA-S. These results indicate that SpA-S is mitogenic for rabbit tissue T cells but will not serve as a T-independent mitogen for rabbit tissue B cells.

Functional anatomy of germinal centers

This year we celebrate the first centennial of the discovery of germinal centers by Flemming in 1884. The present paper reviews and adds new data to the functional anatomy of a germinal center. Emphasizing its reactive nature, we first describe a germinal center reaction and then deal with its infrastructural aspects and constituent cell populations, both lymphoid and nonlymphoid. Elements involved in the de novo formation of a germinal center, like antigen, T cells, and the mysterious germinal-center-precursor cell, are discussed. Next, attention is paid to the requirements for lymphoid cells to migrate into germinal centers, and novel features of germinal-center-seeking cells are presented. Subsequently, we discuss kinetic aspects of the high proliferative activity in a germinal center; and finally a description of the functional capacities of germinal-center-derived cells, such as B memory cells and IgM-antibody-forming cell precursors, completes this picture of present-day knowledge of the germinal center, a structure which has yet to reveal its last secrets.

Germinal centers and the B-cell system. VI. Migration pattern of germinal-center cells of the rabbit appendix

The migration pattern of germinal center cells of the rabbit appendix was studied and compared with that of appendix dome cells, spleen cells, thymus cells and thoracic duct lymphocytes. To discriminate T- and B-cell migration pathways, normal or T-cell-depleted rabbits were used as donors. Cell suspensions were labeled in vitro with 3H-leucine followed by intravenous transfer. The migration of labeled cells in lymphoid organs was studied using autoradiography, particular attention being paid to the spleen of the recipient. B-cells from the appendix dome, spleen and thoracic-duct lymph migrate to primary follicles or the corona of secondary follicles via thymus-dependent areas of peripheral lymphoid organs. In contrast, a B-cell subpopulation from the germinal centers of the appendix migrates to the center of splenic primary follicles and into germinal centers. The migration of germinal center cells to splenic follicle centers is not enhanced by specific antigens. The migration properties of B-cells, possibly changing during differentiation, may be instrumental in the two types of immune reactions, i.e., plasma-cell reaction and germinal-center reaction.