Bs. Baker et al., Skin T cell proliferative response to M protein and other cell wall and membrane proteins of group A streptococci in chronic plaque psoriasis, CLIN EXP IM, 124(3), 2001, pp. 516-521
To determine and compare the T cell response to M protein and other group A
streptococcal (GAS) antigens, T cell lines (TCL) were cultured from the le
sional skin of 33 psoriatic patients and 17 disease controls. GAS-reactive
skin TCL were tested in proliferation assays with recombinant M6 protein, a
nd extracts of cell wall and membrane from type M6 GAS and its correspondin
g M gene deletion mutant. Initially, GAS-reactive skin TCL were obtained fr
om 16 of 25 (64%) psoriasis, and from seven of 17 (41%) control patients. E
leven psoriatic and four control GAS-reactive TCL proliferated to M6 cell w
all extract, whereas all the TCL from both groups responded to the extract
of M6 membrane proteins. This difference in response to the two extracts wa
s significant for both groups of patients (psoriasis, P = 0.0335, controls,
P = 0.0156). GAS-reactive TCL from a further eight psoriasis patients show
ed no difference in response to cell wall extract from M6 GAS (containing t
he M protein minus its C-terminus) compared to that of its corresponding M
gene deletion mutant. Furthermore, GAS-reactive TCL did not proliferate to
recombinant M6 protein. However, a small, but significant reduction in prol
iferation by the eight psoriatic GAS-reactive TCL to the M-negative (lackin
g the M protein C-terminus) compared to M6-positive membrane extract was ob
served (P = 0.01). These findings suggest that GAS-reactive T cells in skin
lesions of chronic plaque psoriasis proliferate to streptococcal membrane
and, to a lesser extent, cell wall proteins. However, psoriatic skin T cell
s do not recognize cell wall M protein.