Psoriasis vulgaris has been recognized lately as an immunologically mediated inflammatory skin disease. To analyze the pathogenetic role of T lymphocytes in the generation of psoriatic skin lesions, 105 T cell clones (TCC) and 10 T cell lines (TCL) were differentially isolated from dermis and epidermis of psoriatic skin specimens. Supernatants prepared from these T cells were studied for their effects on keratinocyte proliferation in vitro. Conditioned media from 14 of 77 epidermal TCC, 7 of which were CD8+, and from 8 of 28 dermal TCC, 5 of which were CD8+, reproducibly enhanced keratinocyte proliferation, with more pronounced mitogenic activities found in dermal TCC. Another 9 epidermal and 3 dermal TCC did not affect keratinocyte growth and supernatants from the remaining clones, as well as from the 5 epidermal and 5 dermal TCL, inhibited keratinocyte replication to varying degrees. Both mitogenic and suppressive activities were largely abolished by addition of an antiserum to interferon-gamma (IFN-gamma), while addition of epidermal growth factor or irradiated psoriatic TCL had little effect on the activities of the supernatants. These studies reveal that a subpopulation of lesional psoriatic T lymphocytes is capable of enhancing keratinocyte proliferation in vitro via secreted products. Their mitogenic capacity most likely requires IFN-gamma, but the ultimate effect is apparently determined by the presence of additional cytokines. Activation of T cells secreting such combinations of factors in vivo may contribute to the keratinocyte alterations characteristic of psoriatic skin lesions.

Psoriasis is an HLA-Cw6–associated T cell-mediated autoimmune disease of the skin that is often triggered by streptococcal angina. To identify keratinocyte proteins, which may become psoriatic autoantigens as the result of an immune response against streptococci, rabbits were immunized with heat-killed Streptococcus pyogenes. Streptococcal immunization induced Ab formation against various human keratinocyte proteins. Sera from psoriasis patients reacted against several of these proteins as well. Common serologic reactivities of rabbits and patients included the proteins ezrin, maspin, peroxiredoxin 2 (PRDX2), heat shock protein (hsp)27, and keratin 6. When used for stimulation of blood lymphocytes, ezrin, maspin, PRDX2, and hsp27 induced increased T cell activation in psoriasis patients, which was particularly evident for HLA-Cw6+ individuals. Ag-specific T cell lines generated with these proteins consisted predominantly of CD8+ T cells and used TCR β-chain rearrangements, which were highly homologous to those expanded within the corresponding skin lesion. Several immunodominant epitopes on the different proteins could be defined according to sequence alignments with the whole genome of S. pyogenes. Our data indicate that maspin, ezrin, PRDX2, hsp27, and potentially keratin 6 could act as autoantigens of a streptococcal-induced autoimmune response and represent targets of the exaggerated T cell response in psoriasis. Additionally, ezrin and hsp27 might constitute antigenic links between psoriasis and inflammatory bowel disease, uveitis, or arteriosclerosis, which are clinically associated.

In various immunological disorders the pathomechanisms of tissue damage are causally associated with specific patterns of locally produced cytokines. To study the molecular and cellular mechanisms involved in the manifestation of psoriasis vulgaris we have assessed the cytokine mRNA profile expressed in lesional psoriatic skin and in T cell clones (TCC) that were established from skin lesions of patients with psoriasis. As demonstrated by use of the polymerase chain reaction (PCR), psoriasis lesions consistently exhibit transcription of a complex pattern of cytokines. It includes mediators selectively produced by T lymphocytes [interferon (IFN)-gamma, tumor necrosis factor (TNF)-beta, interleukin (IL)-2, IL-3 and IL-5] as well as cytokines secreted by various cell types [transforming growth factor (TGF)-alpha/-beta, TNF-alpha, IL-6/-8 and granulocyte-macrophage-colony stimulating factor], while IL-4 is missing. With the exception of TGF-alpha, this cytokine profile was also observed in lesional psoriatic T cell clones yielding supernatants mitogenic for keratinocytes in vitro (MTCC), but not in T cell clones yielding supernatants that inhibited keratinocyte proliferation (STCC). The congruent cytokine expression of psoriatic skin lesions and MTCC emphasizes that inflammation in psoriasis is driven by a sofar unrecognized regulatory T cell subset that may serve to control epidermal regeneration and convey immunosurveillance over epithelial surfaces. It is characterized by the combined expression of IFN-gamma, TGF-beta, IL-2 and IL-5 in the absence of IL-4 and by its selective capacity to enhance keratinocyte proliferation. This newly defined combination of regulatory properties of a distinct T cell population cannot be reconciled with an immune response of the T helper cells (TH)0, TH1 or TH2 type.

Psoriasis vulgaris is a common HLA‐associated inflammatory skin disease. Although its etiology is still unknown, it is thought to involve T cell‐mediated inflammatory mechanisms. In examining the lesional psoriatic TCR β chain (TCRB) usage in a pair of identical twins concordant for psoriasis, we observed repetitive TCR VDJ rearrangements which indicated antigen‐specific oligoclonal T cell expansion. Several of these TCRB rearrangements were identical or highly homologous in the amino acid composition of the complementarity determining region 3 (CDR3), suggesting that T cells with these TCR might be important for disease manifestation. This conclusion was strengthened by TCR analysis of other psoriasis patients. Several repetitive lesional TCRB rearrangements were found that were similar to the conserved CDR3 seen in the twins. Since TCR antigen specificity is largely determined by the β chain CDR3, selection of T cells with conserved TCRB CDR3 motifs could indicate the presence of a common antigen as a major target of the lesional psoriatic immune response.

Psoriasis vulgaris is a common HLA-associated inflammatory skin disease. Although its etiology is still unknown, it is thought to involve T cell-mediated inflammatory mechanisms. In examining the lesional psoriatic TCR beta chain (TCRB) usage in a pair of identical twins concordant for psoriasis, we observed repetitive TCR VDJ rearrangements which indicated antigen-specific oligoclonal T cell expansion. Several of these TCRB rearrangements were identical or highly homologous in the amino acid composition of the complementarity determining region 3 (CDR3), suggesting that T cells with these TCR might be important for disease manifestation. This conclusion was strengthened by TCR analysis of other psoriasis patients. Several repetitive lesional TCRB rearrangements were found that were similar to the conserved CDR3 seen in the twins. Since TCR antigen specificity is largely determined by the beta chain CDR3, selection of T cells with conserved TCRB CDR3 motifs could indicate the presence of a common antigen as a major target of the lesional psoriatic immune response.