Role of t lymphocytes in the humoral immune response. II. T cell-mediated regulation of antibody avidity.

The effect of activated T lymphocytes (ATC) on the avidity distribution of PFC in the secondary response was studied in normal mice. The total PFC response was not significantly changed for either direct or indirect PFC by administration of ATC before secondary antigen challenge. However, marked suppression occurred of indirect PFC that secreted high avidity antibody; no suppression was seen of high avidity direct PFC. At the same time, significant stimulation was seen of relative and absolute frequencies of indirect PFC that secreted middle and low avidity antibody. These effects were dependent on Thy 1-bearing, nylon nonadherent cells which demonstrated carrier specificity. In further characterization of these effects, it was found that increasing the number of ATC transferred produced progressive loss of high avidity PFC and compensatory increase in lower avidity PFC. Moreover, in these experiments, suppression of the high avidity response was inducible with the administration of ATC 5 weeks before to 3 days after the secondary immunization. Thus, it is likely that the avidity-modifying effects are dependent on T lymphocytes which influence the late stages of B lymphocyte maturation.     

Interrelations of cellular and humoral immune response and different doses of sheep erythrocytes in mice]

In experiments on CBA and C57BL/6 mice the generation of antibody-forming cells respectively either in the popliteal lymph nodes or spleen as well as a rate of delayed type hypersensitivity response (DTHR) on the background of subcutaneous (into foot) or intraperitoneal injection of different doses of sheep erythrocytes (from 10(4) to 10(8)) have been studied. In so doing two types of immune response can be isolated on the dependence upon the sensitivity threshold to antigen of DTHR and humoral immunity. Thus in C57BL/6 mice the antigen threshold for DTHR is of one time (in intraperitoneal immunization) or of a two times (in subcutaneous) lower order than for antibody response. In CBA line mice under subcutaneous immunization there can be seen quite an opposite picture while intraperitoneal immunization causes exact correlation of antigen threshold for cellular and humoral immune response.     

Macrophages and T cells control distinct phases of B cell differentiation in the humoral immune response in vitro

The differentiation of B cells in the in vitro PFC-response to red blood cell antigen proceeds through 2 phases. Antigen-reactive B cells acquire the ability to interact with helper T cells in the first phase. This phase is controlled by macrophages through a mediator that they release (Interleukin 1 ([Il-1]). B cells convert into antibody-secreting cells (PFC) in the second phase, which is controlled by helper T cells or by a mediator that they release (T cell-replacing factors [TRF]). This is demonstrated in experiments in which Il-1 increases the number of B cells capable of responding to T cell help. The majority of antigen-reactive B cells reaches that state of differentiation within 40 hr of incubation with Il-1. After this time, the response of B cells depends no longer on the presence of Il-1 but on the presence of T cells or TRF. The presented data suggest that antigen-primed helper T cells (but not unprimed T cells) induce the release of Il-1 by macrophages, thereby also influencing the early phase of B cell differentiation.     

Studies of the immunological capacity of germ-free mouse radiation chimeras. II. Thymus cell function in a humoral immune response to sheep erythrocytes

Experiments described here were undertaken to determine the reason for the depressed humoral immune response in germ-free mouse allogeneic radiation chimeras. Indirect immunofluorescence using the theta (θ) antigen as a marker demonstrated that about 10% of the nucleated cells in the spleen of both allogeneic and syngeneic chimeras bear the θ antigen. One type of in vivo cell transfer assay employed to determine the capacity for “helper” function of thymocytes revealed that allogeneic chimera thymocytes were only 7–18% as efficient in “helper” function as normal thymocytes. A second type of in vivo cell transfer assay demonstrated that the presence of intact normal thymic stroma had no effect on the “helper” inefficiency of thymocytes obtained from allogeneic radiation chimeras.     

Exogenous protease promotes specific antibody forming cell response in vitro

This report presents results from experiments which evaluated the effect of exogenous protease on the in vitro antibody-forming cell (AFC) response of hamster lymphocytes to sheep erythrocytes (SRBC). In the presence of fetal calf serum, trypsin and papain, but not thermolysin, α-chymotrypsin, thrombin, and submaxillary protease, were able to enhance the quantity of AFC which developed. Prior incubation of antigen with proteases had no effect on subsequent antigenicity. The following observations were made: (1) Addition of protease to the culture system enhanced the AFC response only if added in the first 48 hr of the assay. (2) Proteases were able to enhance the development of AFC in lymph node and spleen cell cultures lacking fetal calf serum for 24 hr. (3) When papain was added to spleen cell cultures which normally produce fewer AFC than lymph node cells (LNC) it promoted the development of a 6- to 10-fold increase in AFC causing the magnitude of the response to match the AFC response expected in LNC cultures. These data support a role for a proteolytic event in lymphocyte activation by specific antigens.     

Antipeptide antibody specific for the N-terminal of soluble immune response suppressor neutralizes concanavalin A and IFN-induced suppressor cell activity in an in vitro cytotoxic T lymphocyte response

Soluble immune response suppressor (SIRS) is a nonspecific immunosuppressive lymphokine produced by Lyt-2+ lymphocytes after exposure to Con A, IFN-alpha, or IFN-gamma. The N-terminal 21 residues of SIRS have recently been elucidated and antisera specific for this sequence have been raised in rabbits by using a synthetic peptide coupled to an immunogenic carrier protein. In a series of experiments, we have established that this antiserum blocks the suppressive activity of Con A- or IFN-activated suppressor cells. These data establish that Con A- or IFN-activated suppressor cells exert some or all of their suppressive effects via SIRS. Further studies show that SIRS acts primarily during the induction of CTL and not at the effector phase. Last, we show that SIRS is not involved in the radiation-resistant Ag-specific suppressor cell circuit that can be induced during the in vitro MLR.     

T cell regulation of the immune response to infection in periodontal diseases

Although T cells have been implicated in the pathogenesis and are considered to be central both in progression and control of the chronic inflammatory periodontal diseases, the precise contribution of T cells to the regulation of tissue destruction has not been fully elucidated. Current dogma suggests that immunity to infection is controlled by distinct T helper 1 (Th1) and T helper 2 (Th2) subsets of T cells classified on the basis of their cytokine profile. Further, a subset of T cells with immunosuppressive function and cytokine profile distinct from Th1 or Th2 has been described and designated as regulatory T cells. Although these regulatory T cells have been considered to maintain self-tolerance resulting in the suppression of auto-immune responses, recent data suggest that these cells may also play a role in preventing infection-induced immunopathology. In this review, the role of functional and regulatory T cells in chronic inflammatory periodontal diseases will be summarized. This should not only provide an insight into the relationship between the immune response to periodontopathic bacteria and disease but should also highlight areas of development for potentially new therapeutic modalities.     

Simple sugars with affinity for the macrophage asialoglycoprotein receptor are adjuvants for the humoral immune response to neuraminidase-treated sheep erythrocytes

The influence of monosaccharides on the humoral immune response of mice to normal and neuraminidase-treated sheep red blood cells (SRBC) was investigated. In these studies, both the sugars and antigen were administered i.p. D-Galactose displayed adjuvant activity for neuraminidase-treated but not for normal SRBC. This activity was optimal at an antigen dose of 3 X 10(6) cells. Other monosaccharides with an axial hydroxyl group at position 4 and D-mannose-6-phosphate behaved like D-galactose, whereas structurally unrelated sugars did not. The adjuvant activity of the saccharides corresponded to the affinity of the substances for the asialo-glycoprotein receptor. The adjuvant effects were also expressed in cobra venom factor-treated and C5-deficient mice. This suggests that blockade of the asialo-receptor rather than complement is involved in this form of immunoadjuvant activity. The findings are also in support of our hypothesis that obstruction of nonimmune antigen elimination, in this case at the level of macrophages, would be one of the mechanisms underlying immunologic adjuvant activity.