Perforin hyperreleasability and depletion in cytotoxic T cells from patients with exacerbated atopic dermatitis and asymptomatic rhinoconjunctivitis allergica.

Background: As a plasma membrane pore-forming protein, perforin is essential for T-cell cytotoxicity mediated by lytic granules. Recent studies on the immune system of perforin knockout mice demonstrated striking similarities to the immunopathology of atopic diseases.

Objective: We sought to investigate the perforin system of atopic patients.

Methods: Monoclonal antibodies were used to characterize perforin-positive PBMCs of patients with exacerbated atopic dermatitis (AD) and asymptomatic rhinoconjunctivitis allergica (RCA) by means of immunoflow cytometry. In addition, a perforin release assay was developed to quantify the velocity of ionomycin and phorbol 12-myristate 13-acetate-induced secretion of lytic granules.

Results: In atopic patients significantly fewer lymphocytes contained perforin-positive lytic granules compared with those of healthy control subjects (patients with AD: 14% +/- 5%, n = 13, P <.0001; patients with RCA: 24% +/- 5%, n = 9, P <.01; healthy control subjects: 33% +/- 11%, n = 13). Of all CD8(hi+) cytotoxic T lymphocytes (CTLs), only 18% +/- 9% and 17% +/- 12% were perforin-positive in patients with AD and RCA, respectively, compared with 44% +/- 13% in control subjects (P <.0001). In addition, perforin-positive CD8(hi+) CTLs of atopic patients released their perforin twice as fast and more completely than control CTLs. This means that 50% of initially perforin-positive CD8(hi+) CTLs from patients with AD and RCA released their perforin completely within 32 +/- 16 and 36 +/- 19 minutes, respectively, and an over 85% release was reached within 113 +/- 41 and 118 +/- 60 minutes, respectively. In CTLs of healthy control subjects, however, it took 64 +/- 40 minutes to achieve a 50% release of lytic granules, and an 85% depletion was not reached in 60% of healthy control subjects, even after 180 minutes.

Conclusion: The perforin hyperreleasability explains, at least in part, the decreased percentage of perforin-positive CD8(hi+) CTLs in atopic patients. These distortions in the system of lytic granules of atopic patients may contribute to the functional defects observed in T-cell cytotoxicity in vivo and in vitro in patients with AD and RCA.