The interleukin-1beta (IL-1beta) converting enzyme (ICE) processes the inactive IL-1beta precursor to the proinflammatory cytokine. ICE was also shown to cleave the precursor of interferon-gamma inducing factor (IGIF) at the authentic processing site with high efficiency, thereby activating IGIF and facilitating its export. Lipopolysaccharide-activated ICE-deficient (ICE-/-) Kupffer cells synthesized the IGIF precursor but failed to process it into the active form. Interferon-gamma and IGIF were diminished in the sera of ICE-/- mice exposed to Propionibacterium acnes and lipopolysaccharide. The lack of multiple proinflammatory cytokines in ICE-/- mice may account for their protection from septic shock.

We have developed a simple method for the fractionation of T and B lymphocytes. Plastic dishes coated with antibodies specific for mouse Ig selectively bind splenic B lymphocytes. The adherent cells are easily removed by gentle pipetting; both adherent and nonadherent populations retain immunologic function. In a typical experiment, when 3 X 107 splenic Iymphocytes were added to a 100 X 15 mm plastic dish coated with microgram quantities of anti-Ig, 98% of the nonadherent cells were Ig negative and 97% of the adherent cells were Ig positive. The method is sufficiently sensitive to allow detection and separation of cell types comprising as little as 2% of the total population and can be modified to allow the selection of cells by a double-antibody procedure. We believe that the plastic dish method will be generally useful for fractionating cells on the basis of their cell surface antigens. The ability to fractionate lymphocytes on the basis of surface phenotype has been a major technical advance in the study of the functional diversity of these cells. Many of the methods currently used exploit antibody specificity to separate cells of one type from a mixed population. Cell lysis with antibody and complement is useful only for cell elimination. Separation by affinity column chromatography (1) or fluorescence-activated cell sorting (2) offers the advantage of positive selection by allowing the recovery of both enriched and depleted cell populations.We report a simple and inexpensive method for the separation of B T cell specificity of the serum was determined by complement-dependent lysis of thymocytes and specific immunoprecipitation of T25 (Thy 1 antigen) from thymocyte membranes (5). The cytotoxic titer of this serum was very low (95% of thymocytes were lysed at an antibody dilution of 1:5). Rabbit anti-mouse Ig was raised by repeated subcutaneous injection of DEAE-cellulose-purified mouse Ig in complete Freund's adjuvant. The Ig fraction was purified by ammonium sulfate precipitation (4) and affinity chromatography on Sepharose 4B conjugated with purified mouse Ig (6).Goat anti-rabbit IgG was purchased as serum from SeraSource, Inc., and purified by ammonium sulfate precipitation and affinity chromatography on Sepharose 4B conjugated with DEAE-cellulose-purified rabbit IgG.Normal rabbit IgG was prepared by ion exchange chromatography on Whatman DE-52 ion exchange resin (7).F(ab')2 fragments were prepared by pepsin digestion and gel filtration through Sephadex G-150 (4).Antibodies conjugated with rhodamine were prepared by the method of Cebra and Goldstein (7). Purity of all antibody reagents was determined by sodium dodecyl sulfate/polyacrylamide gel electrophoresis (8) under reducing conditions.All immunoglobulin preparations were centrifuged at 80,000 X g for 1 hr to remove aggregates, sterilized by Millipore filtration, and stored at 4°.Fetal Calf Serum. Fetal calf serum, purchased from Grand Island Biological Co., was heat inactivated at 560 for 2 hr and tested for mitogenic activity on splenic l...

Allotype suppressor T cells (Ts) generated in SJL X BALB/c mice specifically suppress production of antibodies marked with the Ig-1a allotype. The studies presented here show that allotypes Ts suppress by specifically removing helper T cell (Th) activity required to facilitate differentiation and expansion of B cells to Ig-1b antibody-forming cells. We show first that Ts and Th belong to different T-cell subclasses as defined by Ly surface antigens. Ts are Ly2+Lyl- and thus belong to the same subclass as cytotoxic precursor and effector cells; Th are Lyl+Ly2- cells and thus belong to the subclass containing cells which can exert helper functions and initiate delayed hypersensitivity reactions. Placing these cells in these two subclasses shows that Th are different from Ts and suggests that they play different roles in regulating antibody responses. The difference in these roles is defined by the evidence presented here showing that Ts attack Th and regulate the antibody response by specifically regulating the availability of Th activity. We show that in allotype suppressed mice, Ts which suppress Ig-1b antibody production have completely removed the Th activity of helping Ig-1b cells without impairing Th activity which helps other IgB B cells. These findings imply the existence of allotype-specific Th for Ig-1b cells (Ig-1b Th). We directly establish that Ig-1b cells require such help by showing that carrier-primed spleen cells from Iga/Iga congenic hybrids help Ig-1a B cells from hapten-primed Igb/Iga donors but do not help Ig-1b B cells from the same donor in the same adoptive recipient.

The nucleotide sequences of heavy and light chains from 10 monoclonal IgM anti-IgG1 (RF) antibodies were determined and reported here as translated amino acid sequences. Only three families of VK light chains were used in these antibodies: VK1 (two examples), VK8 (three examples), and VK19 (four examples). This represents a significant nonrandom selection of light chains. In contrast, all other variable region gene segments (i.e., VH, DH, JH, and JK) were used in a pattern consistent with random selection from the available pool of germline genes. In two cases, the same anti-IgG1 specificity was generated by a combination of very homologous light chains with unrelated heavy chains. We infer from this that the light chain is the segment used by these antibodies to bind IgG1. The nature of these sequences provides an explanation for the curious observation that as many as 15% of splenic B cells in normal mice may be expressing IgM anti-IgG; if, as our data suggest, certain light chains in combination with many different heavy chains can be used in assembling the anti-IgG specificity, then, because of combinatorial association in which the heavy chain is not relevant for specificity, the fraction of IgM-producing B cells expressing these light chains should approximate the fraction of B cells making IgM anti-IgG. We calculate, based on data presented in several other studies, that 5-17% of B cells express one of the VK types observed in monoclonal RF. This agrees well with estimates for the number of B cells making IgM anti-IgG. In addition, our findings could rule out other explanations of the high percentage of B cells making RF, such as constant stimulation by antigen or presence of numerous antigenic epitopes since it was shown that IgM anti-IgG1 antibodies are not somatically mutated and that they are structurally homogeneous. We aligned the VK sequences of the RF in hopes of finding some primary sequence homology between the represented VK families which might point to residues involved in the binding interaction. Although we found no such homology in the hypervariable regions, we did find significant and unexpected homology in the FR2 and FR3 of these light chains. We noted that these regions are exposed in the Ig structure and postulate that they may be involved in a unique type of binding interaction between two Ig family domains, i.e., VK binding to a constant region domain of IgG.

A/J mice were found to produce autoreactive IgM anti-IgG1 in response to secondary immunization with a number of protein antigens. No anti-IgG1 was produced after a single such immunization, indicating that antigen: IgG1 antibody complexes were responsible for inducing the autoreactive response. The size of the anti-IgG1 response was in some cases massive and of the same order of magnitude as the response to the foreign immunizing material. No significant anti-IgG2a, anti-IgG2b, or anti-IgG3 response was found in mice producing anti-IgG1. Virtually all of the anti-IgG1 material produced was of the IgM class and bound to the Fc region of autologous IgG1. A component of the anti-IgG1 was shown to be able to distinguish between the two mouse IgG1 allotypes. These results suggest that self-reactive anti-IgG is a common component of the secondary immune response of mice that may have powerful physiological and immunoregulatory effects.