Relationship between the synthesis of autoimmune antibodies and the formation of clusters of B, T and APC cells during the syngeneic mixed lymphocyte reaction in BALB/c and NZB mice: a technique for isolation of the spleen autoimmune compartment of non-immunized pathogen-free mice.

Cells from the spleens of non-immunized mice were cultured in horizontal tubes, rotating very slowly around their long axis. Under these conditions, the flux speed gradient of the cell suspension near the tube walls greatly increased the chances of cells coming into contact with one another. Mixed clusters of B, T and APC cells were soon found adhering firmly to the walls of the tube; cluster formation leveled off after about 3 h. The clustered cells were easily separated from those remaining in suspension and constituted a particular cell compartment comprising a maximum of 20-30% of the total. B cells from this compartment, cultured in complete medium for 48 h, almost exclusively produced IgM antibodies. Antibodies reacting with self antigens were so numerous in the culture medium that it is likely all IgM were self antibodies. That the clusters obtained under these conditions constituted a compartment of autoimmune cells is supported by previous work which showed that 20-30% of spleen cells secrete IgM antibodies almost exclusively. Cluster formation as a function of age was compared in NZB mice which are used as a model of lupus erythematosus, and in BALB/c mice which never manifest self-immune pathology. The number of cells found in clusters per whole spleen increased exponentially with age in NZB mice and linearly in BALB/c mice. The production of autoimmune antibodies as a function of age also increased exponentially for NZB mice and linearly in BALB/c mice, which provides further striking support for the hypothesis that the clusters formed constitute the autoimmune comportment.

Fc gamma of IgG: a specific agent of destabilization of lipid bilayers containing oleic acid.

gamma-Immunoglobulins induce the fusion of oleic acid-containing liposomes into tubular structures. An F(ab')2 preparation does not exert the same influence unless it is several orders of magnitude more concentrated. The same is true for several proteins with an isoelectric point higher or lower than the IgG isoelectric point. The Fc of IgG seems thus to exert a specific destabilizing and fusogenic action on artificial lipid membranes. An hypothesis is presented concerning the mode of action of Fc gamma on lymphocyte membrane which is based on the facts mentioned above and on the existence of a phospholipasic activity of Fc gamma membrane receptor.

Temporal evolution of the sensitivity to tetranitromethane of the active site of anti-Tobacco mosaic virus antibodies.

Rabbit anti-TMV antibody taken 9 days after antigen injection is inactivated by much lower concentrations of tetranitomethane (TNM) than anti-body taken after 30 days. This change in sensitivity to TNM occurs in a very heterogeneous population of molecules, including IgM and IgG classes, but the affinity of the antibody remains unchanged. Thus, the phenomenon is not the result of selection of antibody-producing cells under the influence of antigen. Inactivation of early anti-TMV antibody appears to result from the nitration of one tyrosyl residue per Fab fragment. This tyrosine is probably located in the heavy chain and most probably in the variable portion. The moderate sensitivity of late anti-body to TNM is attributed to the lower reactivity of a tyrosine in the active site, and to the fact that nitration of this tyrosine does not inactivate the binding site. The suggested interpretation is that the majority of molecules of a very heterogeneous anti-TMV antibody pool may have a common structure in their active site during the early stage of the antibody response. This may later be replaced in most molecules by different structures.