Excessive costimulation of CD3-dependent lymphocyte response by extracellular matrix proteins in severe widespread psoriasis

Psoriasis and extra domain A fibronectin loops

We have previously postulated that as well as T-helper (Th) 1 and Th17 cells, the transforming growth factor (TGF)-beta/fibronectin (FN)/alpha5beta1 pathway is central to psoriasis pathogenesis. EDA+ FN refers to an alternatively spliced isoform of FN with an additional domain known as extra domain A. EDA+ FN has two important properties pertinent to psoriasis lesions: it stimulates keratinocyte hyperproliferation, and, through stimulation of Toll-like receptor (TLR) 4, stimulates production of proinflammatory cytokines. EDA+ FN production induced by TGF-beta stimulation can be maintained in psoriasis lesions via two main feedback loops. Firstly, EDA+ FN stimulates proliferation of keratinocytes, which, in an autocrine fashion, will release more EDA+ FN. Secondly, EDA+ FN stimulates TLR4 expressed by antigen-presenting cells resulting in the production of proinflammatory cytokines such as tumour necrosis factor-alpha, interleukin (IL)-1, IL-6 and IL-12. The resultant promotion of cutaneous inflammation results in the recruitment of Th1 cells, which also produce EDA+ FN. We propose that these 'FN loops' contribute to the maintenance and progression of psoriatic lesions. Finally, although the association between psoriasis and heart/thrombotic disease remains unclear one plausible link may be the promotion of atherosclerosis and thrombotic heart disease by EDA+ FN.

Profiles of activated T lymphocytes in peripheral blood of Kuwaiti psoriasis vulgaris patients

We have previously reported unexpected immunological features of psoriasis among Kuwaitis, suggesting novel patterns of immune reactivity contributing to the disease. To better define this phenomenon, we herein describe profiles of major populations and immunologically activated subsets of peripheral blood lymphocytes in a cohort of Kuwaiti psoriasis vulgaris patients. Whole venous blood from fifteen psoriatic and twenty eight normal, healthy subjects was analyzed by 2-color flow cytometry for levels of major lymphocyte species and their immunologically activated subsets. When compared to normal subjects, psoriatic blood contained lower cell densities of CD2+, CD8+ (p=0.002 respectively) and B lymphocytes (CD19+) (p=0.003), with a trend toward a lower CD4+ density (p=0.072). Within each major lymphocyte population, activated lymphocytes were present at higher percentages in psoriatic than in healthy blood. These included CD4+ HLA-DR+ (p=0.002), CD4+CD25+ (p=0.043), CD4+CD54+ (p=0.005), CD8+CD25+ (p=0.015), CD8+ HLA-DR+ (p=0.046) and CD3+CD16+CD56+ (p=0.023) Additionally, psoriatic patients were found to have an expanded ratio of memory to naive T cells (CD45RO+CD45RA+) relative to control subjects; this was expected on the basis of increased immune activation. Our findings are consistent with a picture of psoriasis as a disease mediated by activated lymphocytes.