Single administration of lesion-limited high-dose (TURBO) ultraviolet B using the excimer laser: clinical clearing in association with apoptosis of epidermal and dermal T cell subsets in psoriasis.

BACKGROUND/PURPOSE: Development of effective therapy for psoriasis is confounded by numerous factors contributing to disease pathogenesis, including pathogenic immunocytes which appear to drive epidermal keratinocyte hyperproliferation. Our objective was to study clinical and biomarker effects of a single dose of TURBO laser UVB (308 nm) applied directly to psoriatic plaques. METHODS: Eighteen patients with chronic plaque psoriasis received a single dose of 10 minimal erythema dose (MED) UVB and were followed for 8 weeks. Keratome and punch biopsies were assessed for T cell depletion and apoptosis following a single 308-nm dose of UVB. RESULTS: Patients demonstrated clinical improvement as indicated by decreased global Psoriasis Area and Severity Index scores and reduced numbers of pathogenic memory/effector T cells infiltrating lesional epidermis and dermis. Consistent with apoptosis induction, caspase activation increased in lesional T cells after treatment. CONCLUSION: We conclude that a single 10 MED dose of TURBO UVB is effective at reducing the severity and extent of psoriatic lesions. We hypothesize that the reason a single treatment is sufficient to clear a psoriatic plaque is that the 10 MED dose is able to deliver sufficient photons to a microanatomic area of the lesion where susceptible pathogenic T cell mechanisms are operative.

Blockade of CD11a by efalizumab in psoriasis patients induces a unique state of T-cell hyporesponsiveness.

Efalizumab (anti-CD11a) interferes with LFA-1/ICAM-1 binding and inhibits several key steps in psoriasis pathogenesis. This study characterizes the effects of efalizumab on T-cell activation responses and expression of surface markers on human circulating psoriatic T cells during a therapeutic trial. Our data suggest that efalizumab may induce a unique type of T-cell hyporesponsiveness, directly induced by LFA-1 binding, which is distinct from conventional anergy described in animal models. Direct activation of T cells through different activating receptors (CD2, CD3, CD3/28) is reduced, despite T cells being fully viable. This hyporesponsiveness was spontaneously reversible after withdrawal of the drug, and by IL-2 in vitro. In contrast to the state of anergy, Ca(+2) release is intact during efalizumab binding. Furthermore, lymphocyte function-associated antigen-1 (LFA-1) blockade resulted in an unexpected downregulation of a broad range of surface molecules, including the T-cell receptor complex, co-stimulatory molecules, and integrins unrelated to LFA-1, both in the peripheral circulation and in diseased skin tissue. These observations provide evidence for the mechanism of action of efalizumab. The nature of this T-cell hyporesponsiveness suggests that T-cell responses may be reduced during efalizumab therapy, but are reversible after ceasing efalizumab treatment.

Efalizumab (anti-CD11a)-induced increase in peripheral blood leukocytes in psoriasis patients is preferentially mediated by altered trafficking of memory CD8+ T cells into lesional skin.

Therapeutic administration of efalizumab, a humanized antibody to CD11a, induces a marked but reversible increase of peripheral lymphocytes in psoriasis patients. In this study, 13 patients were treated with 12 weekly subcutaneous doses (2 mg/kg/week) of efalizumab, and all 13 patients had increases in leukocyte counts. This increased white blood cell count was mainly due to a 3- to 4-fold increase in the number of circulating CD3(+) lymphocytes during active treatment. Both naive and memory populations of CD4(+) and CD8(+) lymphocytes in the peripheral blood increased, with the largest increase observed in memory CD8(+) T cells. This CD8(+) memory T cell subset is a prominent T cell population found in psoriatic skin. An increase in Type 1 (IFN-gamma producing) T cells was also observed during treatment. Both components of LFA-1, CD11a and CD18, were downregulated during treatment, and surprisingly the integrins CD11b and beta 7 were similarly reduced. We conclude that efalizumab most likely blocks cutaneous entry of memory CD8(+) T cells, a highly disease-relevant cell population. The relatively smaller increase in naive peripheral blood T cells could be attributed to reduced trafficking of naive T cells.