| Abstract
| - We have examined a panel of murine Ly-l+ B lymphomas and purified normal murine peritoneal B cells separated into subsets on the basis of expression of the Ly-1 surface antigen, for their ability to produce cytokines. Where possible, we have used a combination of cytokine detection methods in order to compensate for differences In sensitivity and specificity, and the possibility of Inhibitors masking an activity. All the lymphomas tested were shown to constitutively express TGF-β and CSIFIIL-10. In addition, varying levels of IL-6, TNF-α and TNF-β, and G-CSF, were demonstrable In most of the lymphomas, and variants of one lymphoma (CH12) additionally produced varying levels of IL-α, IL-β, and GM-CSF. FACS purlfled normal Ly-1 + and Ly-lperltoneal B cells, were also shown to express RNA encdlng CSiFIIL-10, ILS, TNF-α and TNF-β, and very low levels of G-CSF, following stimulation with LPS. These data were supported by the detection of IL-6 and CSIFIIL-10 In supernatants from LPS-stimulated Ly-l+ and Ly-1− B cells using specific Immunoassays. None of the lymphomas or B cell preparations produced IL-la, IL-2, IL-5, IL-7, or IFN-γ. The purity of our normal B cell populations was assessed by phenotypic analysis on the FACS and also by the disappearance of certain mRNA transcripts after purification, e.g. CD4, c-fms, GM-CSF, and IFN-γ, most of which could be detected In LPSstimulated total peritoneal cell populatlons. This suggested that our B cell purification method had reduced, to a level undetectable In our assays, contaminatng T cells (CD4), macrophages (c-fms, GM-CSF), and NK cells (IFN-y). Absence of IL-3, IL-4, IL-5, and GM-CSF expression by LPS-stimulated Ly-l+ and Ly-1− B cells reduced the concern that contaminating peritoneal mast cells could account tor the observed cytoklne production. We therefore believe our data provide strong support for production of a subset of cytokines by LPS-stimulated normal B cells. Both the Ly-1+ B lymphomas and normal Ly-1+ and Ly-1+ B cells appear capable of expressing IL-6, TNF-α, TNF-β, and CSIFIIL-10. Thus, while other cytoklnes expressed only by the B lymphomas, e.g. IL-3, IL-4, and GM-CSF (although restricted to the CHI2 lymphomas) may be a resun of transformation, IL-6, TNFα, TNF-β, and CSIFIIL-10 may be important B cell derived immunoregulatory molecules In normal Immune responses Including B cell medlated antigen presentation, autocrine growth of B cells, or B cell medlated irnmunosuppression.
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