Functional subclasses of T-lymphocytes bearing different Ly antigens. I. The generation of functionally distinct T-cell subclasses is a differentiative process independent of antigen.

TLDR

Ly alloantigens encoded by two loci are expressed on thymus‑dependent differentiating lymphoid cells. The study aims to determine whether the Ly‑123+ subclass represents a transitional stage or a distinct differentiated T‑cell subclass with a specific immune role. Peripheral Thy‑1+ cells segregate into Ly‑123+, Ly‑1+, and Ly‑23+ subclasses; Ly‑123+ cells appear first and decline after thymectomy, while Ly‑1+ and Ly‑23+ cells arise later and exhibit distinct helper or cytotoxic functions, demonstrating that functional commitment precedes antigen exposure and correlates with specific Ly antigen expression.

Abstract

Ly alloantigens coded by two unlinked genetic loci (Ly-1 and Ly-2/Ly-3) are expressed on lymphoid cells undergoing thymus-dependent differentiation. Peripheral Thy-1+ cells from C57BL/6 mice can be divided into three subclasses on the basis of differential expression of Ly-1, Ly-2, and Ly-3; about 50% express all three Ly antigens (Ly -123+), about 33% only Ly-1 (Ly-1+), and about 6-8% Ly-2 and Ly-3 (Ly-23+). Cells of the Ly-123+ subclasses are the first peripheral Thy-1+ cells to appear in ontogeny, and are reduced in the periphery shortly after adult thymectomy. In contrast, Ly-1+ and Ly-23+ subclasses appear later in the peripheral tissues than do Ly-123+ cells, and are resistant to the early effects of adult thymectomymperiheral lymphoid populations depleted of Ly-1+ cells and Ly-123+ cells (and thereby enriched for Ly-23+ cells) were incapable of developing significant helper activity to SRBC but generated substantial levels of cytotoxic activity to allogeneic target cells. The same lymphoid populations, depleted of Ly-23+ cells and Ly-123+ cells (and thereby enriched for Ly-1+ cells), produced substantial helper responses but were unable to generate appreciable levels of killer activity. These experiments imply that commitment of T cells to participate exclusively in either helper or cytotoxic function is a differentiative process that takes place before they encounter antigen, and is accompanied by exclusion of different Ly groups, Lu-23 or Ly-1 respectively, from TL+Ly-123+ T-cell precursors. It is yet to be decided whether the TL-phase by Ly-123+ subclass is a transitional form or a separately differentiated subclass with a discrete immunologic function.