Modulation of mitogenic responsiveness by staphylococcal peptidoglycan.

Staphylococcal peptidoglycan can modulate in vivo and in vitro antibody responses and is a B-cell mitogen. The effect of in vivo peptidoglycan treatment on the subsequent in vitro mitogenic responsiveness of mouse splenocytes to phytohemagglutinin, concanavalin A, pokeweed mitogen, and lipopolysaccharide was studied by measuring changes in deoxyribonucleic acid synthesis. Injection of peptidoglycan caused a 100% increase in responsiveness to phytohemagglutinin and pokeweed mitogen and a 45% increase in responsiveness to concanavalin A. Responsiveness to lipopolysaccharide was decreased by 40%. Increased phytohemagglutinin and decreased lipopolysaccharide responses were not due to changes in the kinetics of the response or optimal concentrations of these mitogens. Increased responsiveness to phytohemagglutinin lasted for 2 weeks after peptidoglycan injection. Neither increased background deoxyribonucleic acid synthesis nor changes in the proportion of T cells after peptidoglycan treatment fully accounted for the changes in responsiveness to the mitogens. In vitro costimulation with peptidoglycan and phytohemagglutinin, lipopolysaccharide, concanavalin A, or pokeweed mitogen resulted in interference of the response. Cell separation experiments indicated that peptidoglycan-induced modulation of mitogenic responsiveness was mediated by B lymphocytes.     

Lesions of the medial septal nucleus produce a long-lasting inhibition of T lymphocyte proliferation

The influence of the central cholinergic system on the immune system was studied in Wistar rats by lesioning the medial septal nucleus. This lesion inhibited T cell proliferation of splenocytes and thymocytes induced by the mitogens concanavalin A (Con A), phytohemagglutinin (PHA) and pokeweed mitogen (PWM) up to 25 days and did not affect proliferation at 40 days after lesioning. In contrast, the response to the B cell mitogen lipopolysaccharide from E. coli (LPS) was not affected at any time. These findings suggest a regulatory role of the cholinergic medial septal nucleus on T lymphocyte proliferation.     

Alteration of host defense mechanisms by murine cytomegalovirus infection.

An animal model of a sublethal infection, utilizing murine cytomegalovirus (MCMV), was developed to determine whether immunological factors could contribute to the establishment of a persistent viral infection. Adult female C3H mice inoculated intraperitoneally with 10(5) plaque-forming units of MCMV developed splenomegaly 5 to 12 days after infection. Virus replicated to peak titers (10(3) to 10(6) plaque-forming units per g of tissue) in liver, spleen, lung, kidney, and salivary gland tissue during the acute phase of the infection (3 to 12 days); it then decreased to undetectable levels in all tissues except salivary gland. Serum interferon was detected as early as 12 h after infection, peaked at 36 h (1,093 U/ml), and was undetectable by 4 days after infection. MCMV-infected animals were hyporeactive to interferon induction with New castle disease virus on days 5 to 9 of the infection. Splenic lymphocyte reactivity to phytohemagglutinin and lipopolysaccharide was normal early during the course of the infection, was suppressed during the acute phase of the infection, and had returned to normal by day 18. These data indicate that several parameters of host defense are transiently suppressed during the course of a MCMV infection. The capacity of cytomegaloviruses to alter host resistance may be one factor that contributes to the establishment of a persistent infection.     

Lymphocyte transformation abnormalities in bovine immunodeficiency-like virus infected calves

Bovine immunodeficiency-like virus (BIV) is a lentiviral pathogen of cattle which is genetically and antigenically related to the human immunodeficiency virus (HIV-1). To determine the impact of BIV infection on the bovine immune system we studied the lymphocyte transformation responses of male Holstein calves inoculated with BIV strain R-29 to three mitogens: pokeweed mitogen (PWM), concanavalin A (Con A), and phytohemagglutinin (PHA) at two and six months post-infection. By six months post-inoculation the response to all three mitogens was diminished compared to control animals and remained depressed 10 months post-inoculation. These results demonstrate that a functional impairment of lymphocytes can be observed early in the course of BIV infection, and prior to the onset of overt clinical disease.     

Induction of hamster T cell-specific antiserum in rabbits using hamster brain tissue.

Antiserum specific for hamster thymus-derived lymphocytes, prepared by immunizing rabbits with hamster brain tissue, was cytotoxic to hamster thymocytes greater than lymph node cells greater than spleen cells, while virtually non-reactive against bone marrow. This antiserum inhibited spleen cell response to the T cell mitogen, phytohemagglutinin, but not to lipopolysaccharide, a B cell mitogen.     

Induction of Hamster T Cell-Specific Antiserum in Rabbits Using Hamster Brain Tissue

Antiserum specific for hamster thymus-derived lymphocytes, prepared by immunizing rabbits with hamster brain tissue, was cytotoxic to hamster thymocytes > lymph node cells > spleen cells, while virtually non-reactive against bone marrow. This antiserum inhibited spleen cell response to the T cell mitogen, phytohemagglutinin, but not to lipopolysaccharide, a B cell mitogen.     

Evaluation of the effects of malnutrition and malaria on skin reactions in delayed hypersensitivity to tuberculin, varidase and phytohemagglutinin

The effects of both malnutrition and malarial infection on cell mediated hypersensitivity (CMH) to tuberculin, varidase and phytohemagglutinin (PHA) has been evaluated in a group of children from a rural area of Upper Volta, aged lower than 3 years. Only the response to PHA was decreased during the course of malnutrition. In plasmodium infection associated with a low degree of parasitemia, it appeared that there was no effect on the frequency of positive responses to either these antigens or mitogen at any nutritional conditions. The high prevalence of tuberculin positive test allows to support the interest of a precocious anti tuberculin vaccination.     

Time course characteristics of human herpesvirus 6 specific cellular immune response and natural killer cell activity in patients with exanthema subitum

The time-course of cell-mediated immunity in exanthema subitum is not well documented. The lymphoproliferative response to purified human herpesvirus 6 (HHV-6) antigen and to phytohemagglutinin was measured and natural killer (NK) cell activities determined in three consecutive specimens obtained biweekly from 18 young children and infants with exanthema subitum. Virus isolation and PCR detection of virus DNA and determination of neutralization antibody to HHV-6 and -7 were also carried out. The magnitude of the HHV-6 specific lymphoproliferative response varied; however, in most cases the time course kinetics revealed a low response in the acute phase with a subsequent gradual increase. In contrast, NK cell activities were high in the acute phase and declined gradually during convalescence. The lymphoproliferative response to phytohemagglutinin did not show a consistent trend in kinetics of time; however, dynamic changes in activity were observed in patients during the acute and convalescent periods. The results suggest that NK cells play a major role in resolving acute phase infection while specific lymphocyte activity develops later. The cause of the delayed development of HHV-6 specific lymphoproliferative response is unknown. The lymphoproliferative response to phytohemagglutinin ratios implied that HHV-6 infection has some impact on host T-cell immunity during the course of exanthema subitum.     

New chromosomal abnormality: t(1;19;?) in a case of B-chronic lymphocytic leukemia

Cytogenetic analysis was performed on peripheral blood cells stimulated with interleukin 6 (IL-6), lipopolysaccharide from Escherichia coli (LPS), phytohemagglutinin (PHA), pokeweed mitogen (PWM) and tetradecanoyl-phorbol-acetate (TPA), in a patient with B-chronic lymphocytic leukemia, showing a t(1;19;?) translocation as the sole abnormality. To our knowledge, this translocation has not been described before in any human neoplasia. In this case, the poor response to therapy (survival time 4 months) suggested that t(1;19;?) could be related to an aggressive course of the disease.     

Effect of zinc chloride on hamster lymphoid cells: mitogenicity and differential enhancement of lipopolysaccharide stimulation of lymphocytes.

ZnCl2 over a very narrow concentration range was found to be mitogenic for hamster lymph node cells but not for thymocytes or splenocytes. Maximal leucine, [3H]uridine, and [3H]thymidine incorporation. Addition of 10 micron ZnCl2 was found to greatly enhance the stimulation observed with the B-lymphocyte mitogen lipopolysaccharide but not with dextran sulfate or the T-lymphocyte mitogen lipopolysaccharide but not with dextran sulfate or the T-lymphocyte mitogen concanavalin A. Although not mitogenic for splenocytes, 10 to 25 micron ZnCl2 slightly enhanced lipopolysaccharide stimulation but not concanavalin A or dextran sulfate stimulation. The effect of ZnCl2 on lipopolysaccharide stimulation was also confirmed with outbred Hartley guinea pig splenocytes and lymph node cells. Zinc chloride (50 micron) was mitogenic for both of these tissues; the response to lipopolysaccharide was enhanced by addition of 50 micron ZnCl2, but the concanavalin A response was unaffected. The possibility that the zinc effect is mediated by proteolytic mechanisms is discussed.     

Suppression of lymphocyte transformation by plasma from owl monkeys acutely infected with Plasmodium falciparum.

Plasma collected from owl monkeys during the acute phase of Plasmodium falciparum infection was shown to adversely affect several in vitro responses which are considered to be correlates of cell-mediated immune functions of normal monkeys. In the presence of acute-phase plasma, response of normal monkey peripheral blood lymphocytes to stimulation with phytohemagglutinin, concanavalin A, and pokeweed mitogen was severely reduced, as was the ability of peripheral blood lymphocytes to respond to allogenic and xenogenic histocompatible antigens. The transformation response of peripheral blood lymphocytes from normal humans to phytohemagglutinin and concanavalin A was also suppressed. Since acute-phase plasma was not cytotoxic for peripheral blood lymphocytes, decreased responsiveness did not result from cell destruction. Acute-phase plasma appears to block initial steps in lymphocyte transformation.     

Effects of concanavalin A, phytohemagglutinin, pokeweed mitogen, and lipopolysaccharide on the replication and immunoglobulin synthesis by canine peripheral blood lymphocytes in vitro

Canine peripheral blood lymphocytes (cPBLs) were used to investigate the mitogenic effects of Con A (concanavalin A), LPS (lipopolysaccharide), PHA (phytohemagglutinin), and PWM (pokeweed mitogen) in vitro by measuring tritium-labeled thymidine [( 3H]thymidine) incorporation and immunoglobulin (Ig) secretion. An ELISA specific for canine IgG and IgM showed that cPBLs secreted significantly more IgG than IgM in response to mitogen concentrations from 30,000 to 0.03 ng/10(5) cells. The optimal stimulating dose of mitogen for lymphocyte response measured by IgG secretion was over a much narrower range of concentration than was the [3H]thymidine incorporation measured response. At a concanavalin A dose where there was increased [3H]thymidine incorporation with a decrease in IgG secretion, it appeared that an active suppression of the IgG response was induced.     

Examination of Peripheral Blood Mononuclear Cells and Sera from Thai Adults Naturally Infected with Malaria in Assays of Blastogenic Responsiveness to Mitogenic Lectins and Allogeneic Cell Surface Antigens

We have previously observed that Thai adults who are infected with malaria have a loss of peripheral blood T cells, and that patient sera contain lymphocytotoxic antibodies. In the present study, we examined peripheral blood mononuclear cells from Thai adults naturally infected with Plasmodium falciparum and Plasmodium vivax for the capacity to undergo blastogenesis in response to phytohemagglutinin, concanavalin A, pokeweed mitogen, and allogeneic cell surface antigens in a one-way mixed leukocyte reaction. In addition, sera from actively infected patients were examined with regard to suppressive capabilities toward normal lymphocyte blastogenesis by using the same assays. We found that patient mononuclear cells exhibited normal reactivity to phytohemagglutinin, concanavalin A, and pokeweed mitogen when compared with controls. However, peripheral blood mononuclear cells from patients had a decreased stimulatory capacity in the allogeneic mixed leukocyte reaction, and P. vivax, but not P. falciparum, lymphocytes exhibited decreased responsiveness in the mixed leukocyte reaction. Furthermore, sera from patients with active malaria induced decreased responsiveness by normal mononuclear cells to phytohemagglutinin and concanavalin A, but not pokeweed mitogen; pooled P. falciparum sera caused decreased responsiveness to allogeneic cell surface antigens in the mixed leukocyte reaction. These studies indicate that despite the lost of circulating T cells during the course of infection with malaria, blastogenic responsiveness remains intact, and that sera from patients with malaria are capable of exerting negative immunoregulatory effects.     

Specific and nonspecific NK cell activation during virus infection

The natural killer (NK) cell activation receptor Ly49H is required for resistance to murine cytomegalovirus (MCMV). We show here that NK cell proliferation and production of interferon-gamma (IFN-gamma) was not dependent on Ly49H expression during early MCMV infection. During a later phase of infection, however, Ly49H+ NK cells selectively proliferated and this expansion was blocked by anti-Ly49H administration. With vaccinia virus infection, neither the early nor late phase of NK cell proliferation was selective for Ly49H+ NK cells. These findings indicated that Ly49H+ NK cells were specifically activated by MCMV and that MCMV infection was characterized by nonspecific and specific phases of NK cell activation in vivo.     

T cell hyperproliferation in autoimmunity prone obese strain (OS) chickens is independent of abnormal mitogen binding in vitro and can be demonstrated in vivo

In contrast to systemic autoimmunity, spontaneous autoimmune thyroiditis of Obese strain (OS) chickens is associated with a marked T cell hyperreactivity in vitro, i.e. an increased proliferation and interleukin 2 (IL 2) secretion in response to Concanavalin A (ConA). In the present study we report an enhanced capacity of OS peripheral lymphoid cells (splenocytes and peripheral blood lymphocytes, PBL) to adsorb fluorescein isothiocyante (FITC) labelled ConA, but not phytohemagglutinin (PHA). However, the elevated ConA binding cannot be a prerequisite for in vitro ConA hyperreactivity as OS thymocytes are normal with respect to ConA binding but nonetheless exhibit elevated responses to this mitogen. Moreover, ConA binding does not correlate with the frequency of cells able to express IL 2 receptors upon short term ConA stimulation. The percentage of ConA activatable cells was found to be increased in OS- PBL as compared to normal control PBL, but was unaltered in OS splenocytes. This finding points to a further mechanism of T cell hyperreactivity in OS chicks in addition to the previously reported defects in nonspecific immunosuppression. Finally, enumeration of cells in the S phase revealed that enhanced proliferation of OS T lymphocytes was not restricted to the in vitro response to ConA and phytohemagglutinin (PHA) but also occurs in vivo.     

The ontogeny of interleukin production and responsivity in the frog, Xenopus

The production of and responsivity to leukocyte-derived lymphokine-rich culture supernatants (SNs) was examined during the ontogeny of the frog, Xenopus. Thymocytes and splenocytes from adult frogs are capable of responding to the T-cell mitogen, phytohemagglutinin-P (PHA). Larval thymocytes are unresponsive to this lectin, whereas larval splenocytes are not. PHA-unresponsive thymocytes can be costimulated with PHA plus either a T-cell growth factor (TCGF)-rich SN or an interleukin-1 (IL-1)-rich SN (from cultures of lipopolysaccharide (LPS)-treated macrophage-enriched peritoneal cells (PCs). Stimulation of larval thymocytes with PHA does not produce a TCGF-rich SN as assayed by proliferation of lymphoblasts. Larval as well as adult splenocytes treated with PHA, however, do produce TCGF. These data are consistent with the hypothesis that the factor limiting mitogen responsiveness of larval thymocytes is the ability of cell populations in the thymus to produce rather than respond to either IL-1 or IL-2.     

Memory inflation during chronic viral infection is maintained by continuous production of short-lived, functional T cells

During persistent murine cytomegalovirus (MCMV) infection, the T cell response is maintained at extremely high intensity for the life of the host. These cells closely resemble human CMV-specific cells, which compose a major component of the peripheral T cell compartment in most people. Despite a phenotype that suggests extensive antigen-driven differentiation, MCMV-specific T cells remain functional and respond vigorously to viral challenge. We hypothesized that a low rate of antigen-driven proliferation would account for the maintenance of this population. Instead, we found that most of these cells divided only sporadically in chronically infected hosts and had a short half-life in circulation. The overall population was supported, at least in part, by memory T cells primed early in infection, as well as by recruitment of naive T cells at late times. Thus, these data show that memory inflation is maintained by a continuous replacement of short-lived, functional cells during chronic MCMV infection.     

IgE synthesis in vitro during infection of mice with the nematodeNippostrongylus brasiliensis: Effects of mitogens and antigens

In vitro IgE synthesis by lymphoid cells was studied during the course of infection of mice withNippostrongylus brasiliensis. The studies involved inbred strains of mice which had been shown to be high IgE responders (A.CA, B10.M), or non-responders (Balb/c, B10.D2) to parasite antigen. In addition, F₁ hybrids of low and high responders and irradiated non-responders were studied. Infection withN. brasiliensis led to an increase in IgE synthesis in vitro which was most pronounced during reinfection of mice. Addition of mitogens e.g. pokeweed mitogen (PWM), lipopolysaccharide (LPS), concanavalin A (ConA) to the cultures induced enhancement, suppression or had no effect on IgE synthesis. Addition ofN. brasiliensis homogenate or worm culture supernatant led to a fluctuating pattern of IgE synthesis. No correlation was found between lymphocyte proliferative response to mitogen and worm antigens and IgE synthesis. Our data suggest, that PWM is more likely to enhance IgE synthesis in vitro than LPS or ConA. An enhancement is more easily observed with the cells of non-infected animals or during the early phase of infection or reinfection. The mitogen-induced increase in IgE synthesis did not exceed the values obtained during infection or reinfection.     

Influence of supernatants from polymorphonuclear leucocytes on blastogenesis of syngeneic and allogeneic murine splenocytes.

Supernatant was produced from activated peritoneal polymorphonuclear leucocyte-rich cell populations from different strains of mice. These supernatants were studied for their ability to modify spontaneous and mitogen-induced blastogenesis of syngeneic and allogeneic splenocytes. Our results indicate that polymorphonuclear leucocyte-rich cell cultures from two strains of mice, A/J and BALB/c, produced a supernatant that could enhance PHA-induced blastogenesis of syngeneic and allogeneic splenocytes. Cells from a third strain C57B1/6, did not produce an active supernatant. In general, the response by splenocytes from these three strains paralleled the production of active supernatant that we observed. The response to the active supernatant was dependent upon the mitogen stimulation of the splenocytes, the mitogen dilution and the supernatant activity. These functions are believed to be genetically determined.     

Relationship between in vivo mitomycin c exposure,sister chromatid exchange induction and in vitro mitogenic proliferation. I. Development of murine splenic cell system

In vivo administration of mitomycin C (MMC) to C57BL/6J mice induced a rapid, initial suppression (24 hours post injection) of in vitro mitogenesis. This was followed by of the mitogen concentration–response curves were found for two of the three mitogens, phytohemagglutinin and concanavalin A, but not for lipopolysaccharide. By 144 hours post injection, the dose-response curves and magnitude of the responses had returned to approximately control (untreated) levels. This approach provides a model system for the functional assessment of in vivo cellular damage by MMC.