Antigen-specific synergism in the immune response of irradiated mice given marrow cells and peritoneal cavity cells or extracts

The Anti-Inflammatory Immune Response in Early Trichinella spiralis Intestinal Infection Depends on Serine Protease Inhibitor-Mediated Alternative Activation of Macrophages

Trichinella spiralis is recognized for its ability to regulate host immune responses via excretory/secretory (ES) products. Serine protease inhibitors (serpins) play an important role in ES product-mediated immunoregulatory effects during T. spiralis infection. In this study, the immunoregulatory properties of a serpin derived from T. spiralis (Ts-serpin) were explored in BALB/c mice. The results showed that naturally occurring Ts-serpin was detected in the stichosomes of muscle larvae and adult worms. Moreover, enhancing (by injection of a soluble-expressed recombinant Ts-serpin [rTs-serpin]) or blocking (by passive immunization with anti-rTs-serpin serum) the effects of Ts-serpin changed the levels of cytokines related to inflammation induced by T. spiralis infection in the serum, mesenteric lymph nodes, and peritoneal cavity, which then led to a change in the adult worm burden in early T. spiralis infection. Moreover, the phenotypic changes in peritoneal macrophages were found to be related to Ts-serpin-mediated immunoregulation. Furthermore, a STAT6 activation mechanism independent of IL-4Rα has been found to regulate protein-mediated alternative activation of bone marrow-derived macrophages and mimic the immunoregulatory role of Ts-serpin in T. spiralis infection. Finally, the anti-inflammatory properties of rTs-serpin and bone marrow-derived macrophage alternative activation by rTs-serpin were demonstrated using a trinitrobenzene sulfonic acid-induced inflammatory bowel disease model. In summary, a protein-triggered anti-inflammatory mechanism was found to favor the survival of T. spiralis in the early stage of infection and help to elucidate the immunoregulatory effects of T. spiralis on the host immune response.

Activation of T and B lymphocytes in vitro. II. Biological and biochemical properties of an allogeneic effect factor (AEF) active in triggering specific B lymphocytes

The studies presented herein have focused on the biological and biochemical properties of a nonspecific mediator produced by populations of activated T lymphocytes during short-term in vitro reactions with foreign alloantigens. We have analyzed the activity of the unseparated and of chromatographically separated fractions of the supernatants from such cultures on the in vitro responses of mouse lymphocytes to soluble and macrophage-bound DNP-carrier conjugates and also to particulate heterologous erythrocytes. The results demonstrate that a highly active protein moiety, termed allogeneic effect factors (AEF), in the mol wt range of 30,000-40,000, is capable of acting directly on B lymphocytes, in the presence of antigen, probably to effect triggering and subsequent differentiation and proliferation to antibody-forming cells in vitro. The active molecule, although not manifesting specificity for antigen, does exhibit some strain-specific properties suggesting a possible relationship to cell surface antigens or other gene products coded in the major histocompatibility gene complex.

The development of antigen-binding lymphocytes in foetal tissues

The time of appearance and counts of antigen-binding cells, using radioiodine-labelled flagellin and haemocyanin, was studied in the human and mouse foetus at different gestational ages: the capacity for binding radioiodine-labelled antigens was equated with acquisition of immunological funciton. Cells resembling lymphocytes from human and mouse liver and bone marrow showed antigen binding at early gestational ages, but this binding could not be prevented with species-specific antisera to immunoglobulins. Specific antigen binding to lymphocytes was detected first with thymic lymphocytes, at gestational ages of 12 weeks in humans and 14 days in mice, then with splenic lymphocytes, at 16 weeks in humans and 17 days in mice, and still later with gut lymphocytes. Relative counts of antigen-binding cells in human foetal thymus were maximal at 16–22 weeks and decreased thereafter. Lymphocyte immunocompetence, as judged by the capacity specifically to bind antigen, develops rapidly after the appearance in thymus of cells with the morphology of lymphocytes; this seemed to occur at the equivalent foetal stage in the species studied.

Immunologic memory cells of bone marrow origin. Increased burst size of specific immunocyte precursors

Individual immunocompetent precursor cells of (C57BL/10 x C3H)F(1) mouse marrow generate, on transplantation, three to five times more antibody-forming cells localized in recipient spleens during secondary than during primary immune responses. The increased burst size is immunologically specific since antigens of horse and chicken erythrocytes and of Salmonella typhimurium do not cause this effect in marrow cells responsive to sheep red blood cells. Both sensitized and nonsensitized precursors require the helper function of thymus-derived cells and antigen for the final steps of differentiation and maturation. The burst size of primed precursor cells is the same after cooperative interactions with virgin or educated helper cells of thymic origin. The greater potential of these marrow precursors may be attributable to self-replication and migration before differentiation into antibody-forming descendants. In fact, the progeny cells of primed precursor units are distributed among a multiplicity of foci, whereas those of nonimmune precursors are clustered into one focus. The described properties of specifically primed marrow precursors are those underlying immunologic memory. It remains to be established whether memory cells are induced or selected by antigens and whether the thymus plays a role in this process.

Density gradient separation of marrow precursor cells restricted for antibody specificity

Potentially immunocompetent cells of (C57BL/6 x DBA/2) F(1) mouse bone marrow are committed to antigenic determinants of sheep or burro erythrocytes prior to interaction with thymus-derived cells and participation in immune responses to administered antigens. At this stage of differentiation marrow cells of this particular mouse strain are not yet restricted for the immunoglobulin M or immunoglobulin G antibody class. By equilibrium centrifugation in discontinuous gradients of bovine serum albumin, precursors of cells that produce antibody to sheep erythrocytes migrate to denser regions, whereas the precursors of immunocytes that produce antibody to burro erythrocytes remain in the lower density regions. cursors for all specificities.

Contribution of bone marrow cells and lack of expression of thymocytes in genetic controls of immune responses for two immunopotent regions within poly-(Phe,Glu)-poly-Pro--poly-Lys in inbred mouse strains

Previous cellular studies on the genetic regulation of immunological responsiveness for two immunopotent regions within the branched chain synthetic polypeptide (Phe, G)-Pro--L demonstrated a direct correlation between the number of detectable immunocompetent splenic precursor cells and the response patterns of SJL, DBA/1, and F(1) mice (21). In order to establish the cellular origin(s) of the genetic defect, the present study first demonstrated that thymus and bone marrow cell cooperation was required for (Phe, G)- and Pro--L-specific immune responses. Secondly, limiting dilution experiments, in which several graded and limiting inocula of marrow cells were mixed with a non-limiting number of 10(8) thymocytes and injected into irradiated, syngeneic recipients, indicated that the low responsiveness of the SJL and DBA/1 strains to the (Phe, G) and Pro--L specificities, respectively, could be attributed to a reduced number of precursor cells found in bone marrow. About five times more marrow precursors were detected in SJL mice for Pro--L than for (Phe, G), whereas about five times as many precursor cells were estimated for (Phe, G) as for Pro--L in the DBA/1 strain. These differences are similar to those obtained using spleen cells from unimmunized SJL and DBA/1 donors (21), and indicate that these genetically determined variations in responsiveness can be accounted for by differences in the frequencies of monospecific populations of immunocompetent cells present in bone marrow. In contrast, limiting dilution transfers of thymocytes or thymus-derived cells with an excess of syngeneic marrow cells resulted in equally frequent (Phe, G) and Pro--L responses for both SJL ad DBA/1 strains. This finding in conjunction with the observation that the generation of (Phe, G)- and Pro--L-specific responses were associated in individual recipients injected with limiting inocula of thymocytes indicated that a single population of thymocytes was stimulated by (Phe,G)-Pro--L. Therefore, it is improbable that the thymic population of immunocompetent cells contributes to expression of these genetically controlled defects.

Antigen-specific cells in mouse bone marrow. II. Fluctuation of the number and potential of immunocyte precursors after immunization

Quantitative and qualitative changes of mouse bone marrow cells were studied by limiting dilution assays 2-3.5 months after immunization of donors with sheep erythrocytes or unrelated antigens (Salmonella typhimurium, horse and chicken erythrocytes). Irradiated (C3H x C57BL/10)F(1) mice were reconstituted with an excess of nonprimed thymocytes and small graded numbers of primed bone marrow cells. Direct and indirect plaque-forming cells (PFC) were induced by secondary stimulation with SRBC and enumerated on the 9th day after cell transplantation. Marrow precursors of PFC (P-PFC) cooperated with thymocytes in the production of direct and indirect PFC after SRBC priming. The limiting dilution plots, which were not compatible with predictions of the Poisson model before immunization, changed and conformed to this model afterwards, as if the population of P-PFC had become functionally more homogeneous. The concentration of marrow P-PFC increased up to the 3rd month after priming, and decreased during the 4th, varying over two logarithms of nucleated marrow cells. The fluctuation was simultaneous and of the same order of magnitude for precursors of direct and indirect PFC, which were class restricted. A third effect of immunization was detected at 3.5 months: individual precursor units generated 3-4 times more direct and indirect PFC than at earlier intervals. Qualitative and quantitative changes of marrow P-PFC participating in anti-sheep responses were specific, since antigens unrelated to SRBC failed to induce them. The data suggested that marrow-derived cells were the major carriers of immunologic memory, but that they functioned in cooperation with thymus-derived inducer cells during secondary anti-sheep responses.

Identification by density separation of antigen-specific surface receptors on the progenitors of antibody-producing cells

Initiation of an immune response to sheep erythrocytes by the transplantation of spleen cells into irradiated recipients is thought to involve an interaction between two functionally different lymphoid cells. If such populations actually exist, it should be possible to separate them from each other and to study the properties of each type of cell. To this end, mouse spleen cells have been fractionated using equilibrium centrifugation in density gradients of Ficoll. Two functionally different populations of spleen cells were obtained. Neither population was active in initiating an immune response by itself on transplantation into irradiated mice, but mixtures of the two populations were. One population of spleen cells was also active when transplanted together with normal mouse bone marrow and the other population was active when mixed with thymus cells from normal mice. These results indicate that two different spleen cells must interact to initiate an immune response in vivo.

The specificity of the cell that synergizes with thymus cells was investigated further and shown to have antigen-specific receptors on its surface. These cells can be recognized by their ability to make rosettes with erythrocyte antigens. Thus, the `background' rosette-forming cells found in unimmunized mice are actually progenitors of antibody-producing cells.

Antigen-specific cells in mouse bone marrow. I. Lasting effects of priming on immunocyte production by transferred marrow

Graded numbers of marrow cells and 5 x 10(7) thymocytes were mixed in vitro and transplanted into X-irradiated (C3H x C57BL/10)F(1) mice. Upon injection of sheep or chicken erythrocytes, splenic plaque-forming cells secreting IgM (direct PFC) or IgG (indirect PFC) hemolytic antibody were enumerated at the time of peak responses. Anti-sheep and anti-chicken primary PFC responses elicited by nonimmune marrow cells differed sharply from each other under the conditions of limiting dilution assays. The frequencies of anti-chicken responses in recipients of different numbers of marrow cells conformed to the predictions of the Poisson model, while the frequencies of anti-sheep responses did not. Hence, the function of certain marrow-derived cells was expressed differentially during the two immune responses, to exclude that the same precursor units generated anti-sheep or anti-chicken PFC. The former precursor cells or units were functionally more heterogeneous than the latter. Immunization of marrow donors against sheep erythrocytes did not alter the population of cells engaged in anti-chicken responses, since limiting dilution assays with immune and nonimmune marrow cells gave identical results. However, anti-sheep immunization altered specifically the cell population engaged in anti-sheep responses, in two ways: (a) potentially immunocompetent marrow cells underwent antigen-dependent differentiation or maturation, to become functionally homogeneous. Consequently, the frequencies of PFC responses in limiting dilution assays conformed to the Poisson model; the changes occurred independently in class-restricted precursors of direct and indirect PFC. (b) marrow cells capable of inhibiting precursors of direct anti-sheep PFC arose in primed mice. The inhibition, which was specific, could have been effected directly by marrow cells or by a diffusable product such as IgG antibody. Results indicated that potentially immunocompetent cells of mouse marrow with distinct functions were antigen specific and antigen sensitive.