Characterization of a leukotactic factor derived from psoriatic scale

Area of Science:

• Dermatology
• Immunology
• Biochemistry

Background:

• Psoriasis is a chronic inflammatory skin condition.
• The pathogenesis of psoriatic lesions involves leukocyte infiltration.
• A specific leukotactic factor (PLF) has been isolated from psoriatic scales.

Purpose of the Study:

• To characterize the in vitro properties of PLF.
• To investigate the in vivo biological activities of PLF.
• To elucidate the role of PLF in psoriatic skin changes.

Main Methods:

• Sephadex G-75 chromatography for protein size determination.
• Stability assays (heat, pH, lyophilization, trypsin digestion).
• In vitro leukocyte chemotaxis assays.
• In vivo intradermal injections in humans and guinea pigs.
• Histological examination of skin responses.

Main Results:

• PLF has an approximate molecular weight of 12,500 daltons.
• PLF is heat-stable, resistant to pH extremes, but sensitive to trypsin.
• PLF exhibits strong chemotactic activity for polymorphonuclear leukocytes (PMNs), partially mediated by complement components C3a and C5.
• Intradermal PLF induces erythema, neutrophilia, increased vascular permeability, and epidermal acanthosis in vivo.
• PLF's activity is similar to complement cleavage products and Arthus response.

Conclusions:

• PLF is a potent chemoattractant for PMNs, suggesting its role in psoriatic inflammation.
• PLF's activity is linked to complement activation, particularly C3a.
• PLF is a potential key factor in the development of psoriatic skin lesions and associated tissue changes.