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frican swine fever virus (ASFV) encodes proteins that manipulate important host antiviral mechanisms. Bioinformatic analysis of the ASFV genome revealed ORF I329L, a gene without any previous functional characterization as a possible inhibitor of TLR signaling. We demonstrate that ORF I329L encodes a highly glycosylated protein expressed in the cell membrane and on its surface. I329L also inhibited dsRNA-stimulated activation of NFκB and IRF3, two key players in innate immunity. Consistent with this, expression of I329L protein also inhibited the activation of interferon-β and CCL5. Finally, overexpression of TRIF reversed I329L-mediated inhibition of both NFκB and IRF3 activation. Our results suggest that TRIF, a key MyD88-independent adaptor molecule, is a possible target of this viral host modulation gene. The demonstration of an ASFV host evasion molecule inhibiting TLR responses is consistent with the ability of this virus to infect vertebrate and invertebrate hosts, both of which deploy innate immunity controlled by conserved TLR systems. [ABSTRACT FROM AUTHOR]

Several cloned, non-leukaemic mouse haemopoietic cell lines are believed to be uniquely dependent on interleukin-3 (IL-3) for their survival. All of these lines require the addition of WEHI-3B cell- conditioned medium for their growth. We have examined the growth requirements of four IL-3- dependent cell lines and found that only one, Ea 3.123, is able to grow in medium conditioned by concanavalin A-stimulated rat spleen cells (rat ConACM), whereas the other three, AC2, 32D cl-23 and FDC-P2, are not. Medium conditioned by the growth of concanavalin A-stimulated mouse spleen cells (mouse ConACM) supports the growth of all four cell lines. The Ea 3.123-supporting activity in rat ConACM appears to be of smaller size (∼ 27,000) than the activity in mouse ConACM and WEHI-3BCM (∼ 38,000). The activity is unlikely to be due to GM-CSF, since post-endotoxin serum containing GM-CSF does not support growth of Ea3.123, nor is it likely to be IL-2, since we were able to remove IL-2 by absorption with CTLL-l6 cells without affecting the ability of rat ConACM to support Ea3.123 cells. Our findings have important implications for the assay of IL-3, and mechanisms by which dependent cells respond to IL-3. [ABSTRACT FROM AUTHOR]

The rat monoclonal antibody NIM-R2 has been shown to be directed towards a cell surface differentiation antigen of murine B lymphocytes which is expressed to a greater or lesser extent at different phases of B-cell activation. In this report, NIM-R2 is shown to be capable of modulating the functional capacity of B cells. In the presence of the monoclonal antibody, the ability of fully mature antibody-forming cells to secrete their product is inhibited. This effect is, however, short-lived, with the cells quickly recovering secretory capacity, even in the continued presence of the monoclonal antibody. NIM-R2 also inhibits the generation of antibody-forming cells in culture, the addition of antibody as late as the third day of a 4-day culture period being effective in this respect. The evidence presented here suggests that these inhibitory effects of NIM-R2 are mediated through interference with separate mechanisms. Our data also indicate that, although N1M-R2 inhibits the generation of antibody-forming cells from their B-cell precursors, it does not affect the B-cell proliferative response. The findings are discussed in terms of their relevance to current models of B-cell activation and differentiation. [ABSTRACT FROM AUTHOR]

When normal mice are immunized with rat RBC, autoantibodies to mouse red cells and antigen-specific suppressor cells are generated. Suppressor cell activity is found in T-enriched populations and suppresses only the induction of autoantibody, not ongoing or secondary autoantibody responses. Using anti- bodies lytic for either B cells or distinct T-cell subpopulations, we are able to show that suppression is dependent on the presence of Lyt 1 + T cells. [ABSTRACT FROM AUTHOR]

Cells separated by the fluorescence activated cell sorter on the basis of their surface IgD (sIgD) phenotype have been examined for responsiveness to thymus-dependent and thymus-independent antigens. The ability of monoclonal anti-IgD alloantibodies to inhibit responses in vitro to the various classes of antigen has also been investigated. Evidence is presented indicating that both sIgD positive and sIgD negative cells can respond to all types of antigen tested. However, although the presence of sIgD was necessary for the response of sIgD positive cells to thymus-dependent antigens, the presence of this isotype was not obligatory for the response of the sIgD positive population to thymus independent antigens. The possible role of sIgD as the obligatory purveyor of a B-cell activation signal is discussed in the light of these findings. [ABSTRACT FROM AUTHOR]

The heterogeneity of avidity of DNP binding (rosetting) cells has been studied in mice of various ages, in an attempt to learn more about the development of antibody diversity. The results indicate that during the neonatal period murine B cells show a limited heterogeneity of avidity with no 'high' avidity ABC being detectable. This implies that the full repertoire of anti DNP antibodies is only gradually acquired during ontogeny. The results are interpreted as favoring the hypothesis that somatic events are important in the generation of antibody diversity. [ABSTRACT FROM AUTHOR]

The effect of pre-immunization with soluble haptenated serum proteins or haptenated carbohydrates on the subsequent responses to the hapten in thymus-dependent or thymus-independent form was investigated. In certain cases both thymus-dependent and -independent responses were suppressed whilst in others a differential suppression of thymus-independent responsiveness was observed. These results are discussed in terms of B-cell sub-populations and mechanisms of tolerance induction. [ABSTRACT FROM AUTHOR]

The affinity of anti-DNP antibodies produced by mice of various ages has been studied at the cellular level by the plaque inhibition technique. The affinity of PFC produced shortly after a single injection of antigen was found to increase during the first 6 weeks of life. The responses of 1- and 2-week-old animals also showed apparently restricted heterogeneity. The difference in the affinity of anti-DNP-PFC between young and adult mice could not be attributed to different (serum) levels of antigen or to differences in the rate of maturation of affinity during the immune response. Cell transfer experiments suggested that the age-dependent increase was due to a change in the population of antibody-forming (B) cell precursors and not to a progressive improvement of T-cell function. This finding is interpreted as favouring somatic mutation theories of antibody diversity. [ABSTRACT FROM AUTHOR]

Echinococcus granulosus protoscolex (PSQ infection of BALB/c mice led, after 4 days, to raised numbers of cells forming plaques with trinitrophenyl-treated sheep red cells and bromelain-treated mouse red cells. The findings were similar in athymic and euthymic CBA mice. Activation of B cells was accompanied by secretion of immunoglobulin, as indicated by the reverse plaque technique. In addition, co-culture of PSC with the 7OZ/3 pre-B-cell line led to the induction of differentiation, resulting in the expression of surface immunoglobulin (Ig). It is concluded that E. granulosus is a polyclonal activator of B cells inducing both transformation and differentiation, and that the effect is thymus-independent. [ABSTRACT FROM AUTHOR]

Cross-linking of surface-immunoglobulin (sIg) has been associated with IP3 production and a rise in cytoplasmic-free calcium ([Ca2+]i) in studies of populations of normal and transformed B cells. We have examined the kinetics of the induced cytoplasmic calcium rises in single, Fura-2-loaded cells, during stimulation with a variety of agonists. Our data indicate that the responses of B cells to some stimuli, such as elevated cyclic AMP, consist of repetitive calcium transients, but these Ca2+ oscillations do not occur after sIg ligation. Rather, sIg cross-linking leads to a rapid rise in cytoplasmic calcium which is followed by a sustained elevation. Most of this response seems to result from an inflow of extracellular calcium rather than from internal stores. [ABSTRACT FROM AUTHOR]

The effect of cyclosporin A (CyA) on the response of murine splenocytes to B-cell mitogens, TI-1 and 11-2 antigens was investigated. The proliferative response to LPS was found to be four- to five-fold less sensitive to inhibition than that to dextran sulphate. Antibody responses to a TI-2 antigen in vivo were suppressed by CyA treatment, whereas responses to the TI- 1 antigen DNP-LPS were markedly enhanced. Enhanced antibody responses to DNP-LPS were also demonstrable in vitro in the presence of CyA, and the enhancement was not removed by T-cell depletion. LPS-induced antibody production in vitro was enhanced at the same CyA concentrations that inhibited proliferation by 40-50%. The implications of these findings for the mechanism of action of CyA and for our understanding of B-cell differentiation are discussed. [ABSTRACT FROM AUTHOR]

An autoreactive Tall clone, MTg9B3, specific for mouse thyroglobulin, has been characterized. This clone has properties consistent with it being an autoreactive T helper cell. It is I-A restricted, with a surface phenotype of Thy 1+, L3T4+, Ly2-, and produces a number of non-specific lymphokine activities following specific triggering with antigen. Furthermore, antigen-stimulated clone cells were capable of providing bystander help in SRBC-specific antibody responses. Surprisingly, MTg9B3 cells had a profound suppressive effect on thyroglobulin autoantibody responses in vitro. [ABSTRACT FROM AUTHOR]

Transformation induced by Echinococcus granulosus in unprimed murine spleen cells in vitro was not prevented by rigorous T- or B-cell depletion. When naive T- or S-cell populations were further depleted of macrophages, S-cell transformation was relatively unaffected whereas T-celI transformation was totally inhibited. Peritoneal macrophages from infected mice could present a mitogenic stimulus to purified, naive T- cells, provided that the T- cells had identity in the I region of the H2 complex. K/D identity was neither necessary nor sufficient. It is concluded that transformation can be induced by E. granulosus in both T- and B-cells and that, at least in naive T- cells, the stimulus can be an I region-restricted, macrophage-presented signal. [ABSTRACT FROM AUTHOR]

Male and female progeny of a cross between CBA/N female and BALB/c male mice were tested for their ability to generate autoantigen-specific suppressor cells as a result of stimulation with cross- reacting rat RBC. Male mice, hemizygous for the X-linked defect, were unable to generate these antigen- specific suppressor cells, whereas their female litter- mates behaved like the normal (CBA/Ca × - BALB/c)F1 mice. [ABSTRACT FROM AUTHOR]

The response of bone marrow (B) cells to sheep red blood cells (SRBC) was measured in the presence of thymus-derived (T) cells that had been stimulated by SRBC or RBC from other species. It was found that other RBC, notably pig and rabbit, were much more effective in stimulating T cells for a cooperative response to SRBC than would have been predicted from the very slight cross-reaction between these RBC and SRBC at the antibody level. It is concluded that recognition of antigens at the T-cell level is different, and in this case less specific, than at the level of the B cells. [ABSTRACT FROM AUTHOR]