Journal of Experimental Medicine, Vol 159, 1413-1428, Copyright © 1984 by Rockefeller University Press
Mechanisms of Ly2 suppressor cell activity. Activation of an Ly1 I-J+ cell is required to transduce the suppressive signal
PM Flood and DC Louie
A cell-free product secreted by Ly1-2+ T cells (Ly2 TsF) can suppress the
in vitro response to sheep erythrocytes (SRBC) of spleen cells depleted of
Ly2+ T cells. This suppressor factor expresses biological activity only
when the acceptor cells share major histocompatibility complex (MHC)-linked
polymorphic genes with the cells that made the Ly2 TsF. Removal of Ly1 I-J+
cells from the assay culture abrogates the ability of Ly2 TsF to suppress
these cultures, but we can replace the need for the I-J+ cells in the assay
culture with an I-J+ soluble factor derived from them. We investigated the
cellular interactions involved in the activation of I-J+ cells by Ly2 TsF
in vitro. We have been able to induce the production of an I-J+ molecule
needed for Ly2 TsF activity in a 48-h intermediate culture of B
cell-depleted Ly1 spleen cells, Ly2 TsF, and antigen. This molecule not
only fails to bind antigen, but is also antigen nonspecific in that it can
be induced by Ly2 TsF of irrelevant specificities. In order to replace the
activity of the Ly1 I-J+ cell in the assay culture, the cell induced by Ly2
TsF to produce the I-J+ molecule in vitro must share genetic polymorphisms
linked to the MHC with the Ly2 TsF, and genetic polymorphisms linked to the
Igh-V gene complex with the target cell. In order for Ly2 TsF to induce
cells of the primary culture to produce the I-J+ molecule, Ly2 TsF must
share genetic polymorphisms linked to the IE region of the MHC with the Ly1
I-J+ cell producing the I-J+ molecule. These results indicate that the
suppressive mechanism of Ly2 TsF involves the interaction with an Ly1 I-J+
molecule. This I-J+ molecule serves to focus the antigen-specific
suppressor molecule on the target cell. The recognition event of this
suppressive complex on the surface of the acceptor cell is controlled by
Igh-V-linked genes restricted by the I-J+ molecule of the suppressor
complex. This suppressor interaction is confined to the suppressor effector
phase of the suppressor circuit since the I-J+ molecules needed for by Ly2
TsF activity do not substitute for the I-J+ molecules needed for the
activity of Ly1 TsiF , a T cell factor that initiates the suppressor cell
circuit.(ABSTRACT TRUNCATED AT 400 WORDS)