Abstract
We have previously reported that the sonicate extrast from Actinomyces viscosus T 14 V (Av. sup) causes polyclonal B cell activation (PBA) in murine splenic B cells without any T cell assistance. However, there are some reports describing T cell dependency of PBA induced by A. viscosus in human peripheral blood B cells, and it is still controversial whether or not A. viscosus has the capability of exhibiting PBA without the help of T cells.
In this report, we examined PBA in human peripheral blood B cells using the same Av. sup which induced T cell independent PBA in murine splenic B cells. The PBA was evaluated in terms of immunoglobulin (Ig) production by means of micro-ELISA method and cell proliferation by incorporation of 3H-TdR after incubation of cells for 5 or 7 days with Av. sup. Human peripheral blood B cells were highly purified by the following methods; The peripheral blood was collected by venipuncture and the peripheral blood mononuclear cells were harvested using gradient centrifugations. These cells were passed through a Sephadex G-10 column, and T cells were eliminated by rosette formation with sheep red blood cells. B cells were highly purified from these T celldepleted cell populations by panning method with anti-human Ig antibody coated dishes followed by complement-dependent cytotoxisity using monoclonal antibody cocktails consisting of OKT 3, OKT 4 and OKT 8.
These highly purified B cells could not respond to T cell mitogens such as PHA. The Av. sup did induce both cell proliferation and Ig production both in human peripheral blood mononuclear cells and peripheral blood lymphocytes, while it did not induce PBA in highly purified human peripheral blood B cells without the participation of T cells. However, reintroduction of T cells into B cell cultures restored significant PBA by Av. sup. Moreover the addition of macrophage fractions allowed further PBA by Av. sup.
These results indicate that the presence of T cells may be necessary for A. viscosus-induced PBA in human peripheral blood B cells (i.e. T cell-dependent PBA). It also suggested that the interactions of immunocompetent cells influenced the A. viscosus-induced PBA in human peripheral blood B cells.
