Figure 4.

Reduction in tonsil cell immunoglobulin release in response to streptococcal pyrogenic exotoxin (SpeA). Tonsil cells were stimulated for 1 week with recombinant SpeA 100 ng/ml (blue) or unstimulated control (black) and supernatants harvested daily from days 1 to 8 of culture (a). Harvested supernatants were then analysed by enzyme‐linked immunosorbent assay (ELISA) for the presence of total immunoglobulin (Ig)G. Means and standard deviation (s.d.) of experimental triplicates from a single donor are shown at each time‐point, representative of five different donors. SpeA significantly reduced tonsil cell production of immunoglobulin (Ig)G (b, n = 16 donors, P = 0·0005***); IgA (c, n = 8 donors, P = 0·0078**); and IgM (d, n = 7 donors, P = 0·0156*) in comparison to unstimulated cultures, when a wider pool of donors was tested after 7 days of co‐incubation with SpeA. Horizontal bars represent median values. Non‐SpeA‐exposed control tonsil histocultures from seven donors produced large quantities of IgG (ng/ml), and this was diminished by co‐culture with SpeA (e) P = 0·014* (all Wilcoxon’s paired signed‐rank t‐test).