In Vitro Methotrexate as a Practical Approach to Selective Allodepletion

Kinetics of T cell growth in MLR and MTX blockade. (A) Representative dot plots of a primary MLR. CFSE staining is shown on the X-axis and CD8 staining on Y-axis. The data are gated to show CD3⁺/CD4⁺/CD8⁻ or CD3⁺/CD4⁻/CD8⁺ cells; thus, the CD8⁻ populations represent CD4⁺ T cells. The gray populations to the right represent nondividing cells. The dividing cells are shown in red (CD4⁺ T cells) and green (CD8⁺ T cells). The numbers represent the proliferating fraction of CD4⁺ and CD8⁺ cells, respectively. As indicated, the top row is an autologous control, the middle row is an alloreaction, and the bottom row is the SEB-stimulated positive control. Each column represents the indicated day of culture. Data is representative of 5 replicate experiments. The lower 2 panels show the percent proliferation of CD4⁺ (B) and CD8⁺ (C) T cells at days 2, 3, 5, and 7 in an autologous control, an alloreaction, and an MTX-treated alloreaction. The mean (SEM) of 5 separate experiments is shown. Thus, MTX blocked the proliferation of both CD4⁺ and CD8⁺ T cells on all days.

Methotrexate inhibits proliferation of alloreactive T-cells. (A) Representative dot plots of an autologous reaction, an alloreaction, and an MTX-treated alloreaction at days 5 and 7 of culture. The layout is similar to that of Figure 1, with numbers representing CD4⁺ and CD8⁺ proliferation. Data is representative of 14 replicate experiments. (B, C) The cumulative data from the 14 experiments, represented as mean ± SEM of CD4⁺ (B) and CD8⁺ (C) T cell proliferation. MTX significantly inhibited both CD4⁺ and CD8⁺ T cell proliferation in primary MLRs (P < .001).

Methotrexate suppresses proliferation of all dividing T-cells. (A) Representative dot plots demonstrating the proliferation of CD4⁺ and CD8⁺ T cells in SEB-stimulated cultures in the presence (bottom row) or absence (top row) of MTX. (B, C) Cumulative data from 14 experiments, demonstrating that MTX significantly inhibited SEB-induced proliferation of both CD4⁺ and CD8⁺ T-cells.

Methotrexate does not affect activation of T cells in MLR. (A) Representative dot plots of CD25 expression on T cells on day 7 of a primary MLR in the presence (bottom row) or absence (top row) of MTX. CD4⁺ T cells are shown in the left column, whereas CD8⁺ T cells are shown in the right column. CFSE staining is shown on the X-axis and CD25 staining on the Y-axis. The populations on the right represent nondividing cells. The threshold for CD25 expression was set using an isotype control antibody. The numbers represent the percentage of cells located in each quadrant. (B, C) Cumulative data from 14 replicate experiments. The graphs represent the mean (+SEM) percentage of CD25⁺/nondividing cells for the indicated culture conditions and cell types (n.s. = not significant).

Methotrexate treatment of primary MLR results in selective allodepletion with preservation of third-party and antiviral responses. (A) Representative dot plots of a secondary MLR, using responder cells isolated from a primary alloreaction that was either untreated (top row) or treated with MTX (bottom row) for 7 days. The stimulators were either the autologous control, the same allostimulus , a “third-party” allostimulus, or CMV antigen (as indicated). (B, C) Cumulative data from 12 separate secondary MLRs. The mean proliferation (+SEM) of CD4⁺ (B) and CD8⁺ (C) T cells are shown, under the indicated culture conditions. Thus, MTX treatment resulted in selective inhibition of responses to the same allostimulus, whereas leaving intact responses to third-party stimuli as well as a viral antigen.