Effect of extracorporeal photopheresis on selected immunologic parameters in psoriasis vulgaris.

Extracorporeal photopheresis (ExP) was administered every other week in an outpatient setting to four patients with chronic refractory psoriasis vulgaris without arthropathy. The duration of treatment ranged from six to 13 months. Two patients received methotrexate concomitantly during the initial phase of the study. All patients demonstrated a decrease in erythema, induration, and scaling of lesional skin, accompanied by incomplete clearing of lesions such that the percentage of involvement (SI) ranged between 40 to 80 percent of baseline scores. Exacerbations of psoriasis occurred with minor provocations, and two patients who were predisposed to developing epithelial skin neoplasms as a consequence of prior treatments continued to develop tumors during the study interval. Prolonged ExP treatment was otherwise well tolerated, without evidence of toxicity on routine laboratory safety tests or changes in lymphocyte counts. All patients, however, exhibited decreased intradermal skin responses to recall antigens and a decreased capacity of peripheral lymphocytes to produce interleukin 2 (IL-2) in response to polyclonal stimuli in vitro. These observations suggest that the observed anti-inflammatory effect of alternate-week ExP on psoriasis is mediated in part to a direct inhibition of lymphokine production or release by psoralen-ultraviolet-exposed lymphocytes.

Dietary ascorbic acid and resistance to experimental renal candidiasis.

Guinea pigs were maintained for various periods of time on low (0.5 mg/day), intermediate (20 mg/day), or high (100 and 500 mg/day) levels of dietary ascorbic acid. Animals in each experimental group were challenged with Candida albicans via cardiac injection, and the course of infection in the kidneys was assessed. The results show that the animals receiving only 0.5 mg of ascorbic acid per day were significantly more susceptible to the infection than animals maintained on any higher level of dietary ascorbic acid. The greater susceptibility of the guinea pigs in the 0.5-mg level group was evident, however, only during "early" stages of the infection (until about day 3). Guinea pigs receiving high levels of dietary ascorbic acid were no more resistant at any time after infection, or with any challenge dose, than those receiving an intermediate dietary level. Although these data suggest that vitamin C may be involved in resistance to candidiasis, tissue levels of ascorbic acid do not change significantly with time after infection. These results indicate that low levels of dietary ascorbic acid increase susceptibility to candidiasis, yet high (or "megadose") levels of dietary vitamin C do not show any effect on resistance to this microorganism.