Antigen leakage from immunosorbents. Implications for the detection of site-directed auto-anti-idiotypic antibodies

Lipopolysaccharide-induced IgM production is not suppressed by antigen receptor ligation in B cells from some autoimmune strains of mice

Ligation of surface immunoglobulin on resting or activated nonautoimmune B cells inhibited lipopolysaccharide (LPS)-induced total IgM production. B cells from NZB, (NZB x NZW)F1, and BXSB mice were relatively resistant, but B cells from NZW or MRL/lpr mice were inhibited. The resistance occurs in B cells from young and old NZB mice, and in both resting and activated splenic NZB B cells. Anti-ssDNA responses induced by lipopolysaccharide occur in the presence of antigen-receptor-ligating antibody in NZB, but not in DBA/2, B cells. Antagonism in signaling between the antigen and LPS receptor is not a general B cell hyporesponsiveness, but defects in antagonism specifically between antigen and LPS signaling may be a predisposing factor to autoimmune disease in some autoimmune strains of mice.

Immunoregulatory characteristics of the in vitro anti-ssDNA response

Continuous blockade of B-cell antigen receptors (BCRs) with Fab alpha sIg prevents the anti-ssDNA response of high, but not low, density B cells. Signaling via the BCRs, by prior exposure to crosslinking F(ab')2 alpha sIg, had no effect on the spontaneous anti-DNA response, but prevented a lipopolysaccharide-induced anti-DNA response. Pretreatment with intact alpha sIg, which provides exogenously derived Fc signals, reduced the response. An Fc-signal-blocking agent, F(ab')2 anti-IgG-Fc antibody, increased the number of anti-DNA antibody-forming cells produced in the absence of exogenous IgG anti-ssDNA antibody. Thus, activation is dependent on the availability of the BCRs, prior BCR crosslinking does not interfere with activation, and endogenous IgG anti-ssDNA antibody limits the activation of anti-ssDNA-specific B cells most of which are T-cell independent. These results indicate that the anti-ssDNA response is driven through the BCR.

Blockade of immunoregulatory Fc-signalling by HIV peptides: oligopeptides from HIV gp120 and gp41 bind the Fc portion of IgG and increase the in vitro anti-ssDNA response

Concomitant ligation of antigen receptors with Fc-receptors negatively signals B cells. Antibodies to the Fc portion of IgG prevent this negative Fc-signalling, provided that these antibodies do not emit Fc signals. Prevention of Fc signals leads to augmented antibody responses to self and foreign antigens, and reduces the requirement for T cells by 10- to 100-fold in T cell-dependent antibody responses. In ELISA assays, peptides from conserved portions of the glycoproteins, HIV-1 gp120 or gp41 from HIV-1 and HIV-2 bind to the Fc portion of IgG, but do not bind the F(ab')2 portion of IgG. HIV-derived peptides, which bind to the Fc portion of IgG, augment the antibody-forming cell response to single-stranded (ss)DNA. The spontaneous response to ssDNA using spleen cells from young mice, and the response in the presence of exogenous DNA using spleen cells from old mice, are augmented to the greatest extent. These results demonstrate that HIV peptides bind to the Fc portion of IgG and augment immune responses to DNA; they suggest the possibility that blockade of the Fc portion of IgG antibodies is associated with a reduction in Fc-mediated regulation of anti-self responses. Blockade of regulatory Fc-signalling may account for increased circulating immunoglobulins and autoantibodies in clinical AIDS.

Characterization of immune complex components by dot blot analysis

A method is described for the characterization of immune complex components by dot blot analysis. After isolation by chromatographic techniques and precipitation with polyethylene glycol, immune complexes were dissociated in 0.1 M phosphate (pH 2) and bound to a nitrocellulose membrane in a dot blot unit. Biotinylated probes were then used to identify the following immune complex components: specific antigens, biologically active antibodies, antibody isotypes, antibody subclasses, antibody idiotypes, and rheumatoid factors. This nonradioactive procedure takes less than 2 h to perform and has been used to analyze immune complexes isolated from sera (rabbit and human) and synovial fluid (human).

Role of interferon-gamma in the modulation of the IgE response by 2,4-dinitrophenyl-Bordetella pertussis vaccine in the mouse

Immunization of mice with 2,4-dinitrophenyl-Bordetella pertussis (DNP-BP) failed to induce anti-DNP IgE responses. Administration of DNP-BP induced, however, the formation of anti-DNP IgE B memory cells, as demonstrated by adoptive transfer. Furthermore, mice pretreated with DNP-BP and primed with 2 micrograms DNP-ovalbumin (OA) in alum 2 weeks later produced high day-7 anti-DNP IgE levels. These subsided to near undetectable levels by day 12-14. The transient expression of serum IgE levels was accompanied by normal levels of anti-DNP IgG. The anti-OA response induced as a result of priming with DNP-OA in alum was not affected by pretreatment with DNP-BP. IgG subclass analysis revealed that mice pretreated with DNP-BP had elevated levels of IgG2a and reduced levels of IgG1 as compared to control (TNP-keyhole limpet hemocyanin-pretreated) mice. Treatment of mice with an anti-interferon-gamma monoclonal antibody, shortly after immunization with DNP-BP, not only reduced anti-DNP IgG2a levels, but prevented the sharp anti-DNP IgE decline that occurred after priming with DNP-OA in alum. These results suggest that DNP-BP-induced interferon-gamma production modulates Ig isotype expression in vivo in an anti-gen-specific manner.

Detection of antibody, idiotype, and anti-idiotype forming cells by in situ immunocytochemical staining

Methods are described for the immunocytochemical staining of cryostat sections of lymphoid tissue with enzyme conjugates of antigen, idiotype (Id) and anti-idiotype. Results established this as a useful approach, for simultaneously detecting Id and anti-Id antibody forming cells (AFC) in situ. As a model, the 5AF6 Id family associated with the BALB/c mouse antibody response against the p-azophenyl-arsonate (Ar) epitope was examined by two-color immunocytochemical staining, allowing the simultaneous detection of both Id+ and Id- anti-Ar AFC. Spleens from mice secondarily immunized with Ar antigen but not normal mice contained anti-Id AFC stained with the 5AF6 Id but not with another immunoglobulin of the same isotype. A sequential staining method was developed which allowed the detection of both Id and anti-Id AFC in the same tissue, thus providing a means of examining Id and anti-Id antibody networks in intact lymphoid tissues.