Expansion of activated human naïve T-cells precedes effector function

Abstract

Naïve T-cells divide and mature, both functionally and phenotypically, upon stimulation through the T-cell receptor. Although much is known about the overall changes that occur in naïve cells upon TCR stimulation, and the different memory/effector populations that arise following stimulation, the relationship between cell division and functional and phenotypical changes that occur after activation is poorly understood. Here, we examine the early stages of human naïve and antigen-experienced T-cell activation, and the relationship between cell division and acquisition of effector function during the transition from resting antigen-experienced or naïve T-cells into effector cells. Stimulated naïve T-cells proliferate prior to acquisition of effector function, as measured by cytokine production and expression of effector-associated cell surface molecules. Additionally, we show that interlukin-7 (IL-7) can drive proliferation of naïve T-cells without TCR:MHC peptide interactions. IL-7 alone does not, however, drive the proliferation of antigen-experienced T-cells. Memory T-cells will divide in response to exogenous IL-7 but only in the presence of naïve T-cells and IL-2. This study contributes to the current understanding of the mechanistic differences between naïve and memory T-cell responses by defining the functional and phenotypic changes that occur to T-cells after stimulation.

Fig. 1

Cell division of stimulated naïve T-cells precedes effector function. Cord blood PBMC were stained with 0·25 µm CFSE and stimulated with PHA or SEB for 4 days, or were stimulated by MLR for 6 days. Panels demonstrate surface marker expression and cytokine production with respect to cell division for CD4+ or CD8+ gated naïve T-cells.

Fig. 2

.Stimulated antigen-experienced T-cells gain effector function without cell division. PBMC from healthy adult donors depleted of CD45RA+ T-cells, were stained with 0·25 µm CFSE and were then stimulated for 4 days with PHA or SEB, or for 6 days by MLR. Shown is a dot plot panel of surface markers and cytokine production for antigen-experienced CD4+ or CD8+ gated T-cells.

Fig. 3

IL-7 drives proliferation of naïve T-cells in MHC independent fashion. Cord blood PBMC were stained with 0·25 µm CFSE and were then cultured for 9 days in 10 ng/ml IL-7 with isotypic control antibodies (a) or 10 µg/ml blocking antibodies recognizing HLA A, B, C, DR, DP, and DQ (b) Dot plots of CD4+ or CD8+ gated T-cells show expression patterns of CD45RA, and CD45RO with respect to cell division. Boxed areas of CD4 and CD8 plots represent the percentage of cultured cells that had proliferated more than three times for IL-7 alone (a) and IL-7+ anti-MHC antibodies (b).

Fig. 4

IL-2 is Required for IL-7 induced expansion of memory T-Cells present in umbilical cord blood. Cord blood PBMC were stained with 0·25 µm CFSE and were then cultured for 9 days in 10 ng/ml IL-7 with or without 10 µg/ml depleting antibodies to IL-2. After culturing, PBMC were stained with CD4 and CD45RO or CD45RA, and CD8 and CD45RA or CD45RO. Dot plots of CD4+ or CD8+ T-cells show expression patterns of CD45RA, CD45RO, CD25, and IFN-γ with respect to cell division.