Fig. S1. T cell proliferation following 7-day co-culture with activated B cells. Carboxyfluorescein diacetate N-succinimidylester (CFSE) dilution was determined in CD4+ T cells after 7-day co-culture activated [anti-CD40, 1 μg/ml + interleukin (IL)-4, 10 ng/ml, for 48 h] B cells. (a) T cell proliferation detected upon 7-day co-culture with activated and calcitriol primed, as indicated in the figure, B cells. (b) T cell proliferation upon 7-day co-culture with activated B cells in the presence of increasing concentrations of toxic shock syndrome toxin 1 (TSST-1). Data represent four to five independent experiments and analysed using the analysis of variance (anova) test. Data are shown as mean ± standard deviation. *P ≤ 0·05; **P ≤ 0·01; ***P ≤ 0·001 are considered significant.

Fig. S2. No relevant calcitriol spillover from B cell culture into T–B cell co-culture. The human promyelocytic leukaemia HL-60 cell line was incubated with calcitriol 1 μmol/l–100 pmol/l (upper plots) or supernatants from anti-CD40 (1 μg/ml), interleukin (IL)-4 (10 ng/ml) preactivated and calcitriol (as indicated in the Figure)-treated B cells; 48 h preactivation following washing and additional incubation with RPMI-1640 medium for 1 and 3 days. Supernatants were tested for calcitriol spillover with calcitriol-dependent expression of CD38 by the HL-60 cell line.

Table S1. Primer sequences for quantitative polymerase chain reaction (qPCR).

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