[Relationship between serum interleukin-4 or interferon-gamma level and B cell abnormality in patients with collagen...

The role of interleukin-4 (IL-4) and interferon-gamma (IFN-gamma) in the pathogenesis of the collagen vascular diseases was studied. The serum level of IL-4 was decreased in patients with systemic lupus erythematosus (SLE) and mixed connective tissue disease (MCTD), and was variable in patients with rheumatoid arthritis (RA). The serum level of IFN-gamma was increased in patients with SLE, MCTD and RA. In patients with SLE, there was an inverse correlation between the levels of IL-4 and IFN-gamma. The proliferation and immunoglobulin production of the high-density-B cells in response to IL-4 was suppressed in normal controls, although the degree of suppression was less in patients with SLE. Cell cycle analysis using ethidium bromide demonstrated the similar findings. These data suggest that IL-4 and IFN-gamma might participate in regulating both of growth and differentiation of B cells in vivo. However, immunoglobulin production by whole B cells in response to IL-2 or PHA-induced T-cell factor was extensively facilitated by IFN-gamma in patients with SLE. It is possible that IFN-gamma enhances the differentiation of already-activated B cells, and that polyclonal B cell activation is promoted. Therefore, the failure of the regulatory mechanism by these cytokines might be related to the pathogenesis of these diseases.