title: Identification and quantitation of interferon-gamma producing T cells in psoriatic lesions: localization to both CD4+ and CD8+ subsets.
abstract: Interferon-gamma (IFN-gamma) produced by lesional T cell clones is critical for the induction into G1 of the cell cycle by psoriatic keratinocyte stem cells; however, direct data demonstrating psoriatic lesional T cell subset IFN-gamma expression, and quantitation at a single cell level to calculate in vivo proportions, are lacking. In this study, using flow cytometry of freshly isolated normal and psoriatic lesional T cells from keratome biopsies, we found elevated CD3+, CD4+, and CD8+ T cells in all compartments of psoriatic skin, compared with normals. Using Brefeldin A to induce short-term intracellular accumulation of IFN-gamma in T cells capable of IFN-gamma production, we found that 90% of psoriatic patients have IFN-gamma-producing T cells at a greater proportion of their CD3+ cells than normals, with a mean of 16%+/-3%, as compared with 4%+/-2% in normal epidermis (p = 0.01). Expressed as density in the tissue, the IFN-gamma+ CD3+ cell number in psoriatic epidermis was 97+/-22 per mm2 surface area, as compared with 4.4+/-1.8 per mm2 of normal epidermis (p = 0.002). Thus, the total number of IFN-gamma+CD3+ T cells in the skin of a patient with 20% involvement is estimated to be 3.9 x 10(8). CD4+ and CD8+ IFN-gamma+ T cells were both elevated in psoriatic epidermis (p = 0.04 and p = 0.008, respectively) relative to normal skin. In the dermis, only 44% of patients demonstrated a higher percentage of IFN-gamma-producing T cells than did normals (p = 0.1), possibly indicating dilution, in some patients, by fresh infiltrating T cells. Interleukin-4 was not found by a combination of flow cytometry, reverse transcriptase-polymerase chain reaction, western blot, and immunoprecipitation. In conclusion, a significant portion of lesional T cells in psoriasis are IFN-gamma producing, without interleukin-4. The increased numbers of both IFN-gamma+CD4+ and IFN-gamma+CD8+ T cells indicate that both CD4+ and CD8+ IFN-gamma+ T cells are present in appropriate anatomic locations to sustain the lesional pathology.
authors.affiliation: Department of Dermatology, Case Western Reserve University, University Hospitals of Cleveland, Ohio 44106, USA.
authors.forename: S K
authors.initials: SK
authors.lastname: Szabo
authors.forename: C
authors.initials: C
authors.lastname: Hammerberg
authors.forename: Y
authors.initials: Y
authors.lastname: Yoshida
authors.forename: Z
authors.initials: Z
authors.lastname: Bata-Csorgo
authors.forename: K D
authors.initials: KD
authors.lastname: Cooper
mesh_terms: D000328:Adult; D017252:CD3 Complex / Q000032:analysis; D015496:CD4-Positive T-Lymphocytes / Q000737:chemistry; D018414:CD8-Positive T-Lymphocytes / Q000737:chemistry; D000078404:Epidermal Cells; D005260:Female; D005434:Flow Cytometry; D006801:Humans; D007371:Interferon-gamma / Q000378:metabolism*; D015847:Interleukin-4 / Q000378:metabolism; D018655:Lymphocyte Count; D008297:Male; D008832:Microchemistry; D008875:Middle Aged; D011565:Psoriasis / Q000378:metabolism* / Q000473:pathology*; D012867:Skin / Q000033:anatomy & histology / Q000166:cytology / Q000276:immunology; D013601:T-Lymphocytes / Q000166:cytology / Q000378:metabolism*
chemical_list: D017252:CD3 Complex; D015847:Interleukin-4; D007371:Interferon-gamma