Early preservation of effector functions followed by eventual T cell memory depletion: a model for the delayed onset of the effect of thiopurines

OBJECTIVE

The onset of the effect of thiopurines is delayed for several months. The aim of this study was to investigate immune mechanisms for this delay.

METHODS

The effects of thiopurines on human peripheral blood T cells and on lamina propria lymphocytes were investigated for apoptosis induction by Annexin V/propidium iodide (PI) and for cytokine secretion by intracellular staining and ELISA assays. To investigate the mechanism of the effect of thiopurines in vivo, Balb/C mice were co-immunised with HEL/OVA (hen egg lysozyme/ovalbumin) antigens, and then repeatedly challenged by HEL only, while being treated by mercaptopurine or vehicle alone for either 4 or 20 weeks. The memory response of CD4+ splenocytes towards HEL/OVA was then determined by CFSE (carboxyfluorescein succinimidyl ester) dilution.

RESULTS

Thiopurines arrested the proliferation of stimulated T cells but did not enhance the apoptosis of either resting T cells or activated T cells until day 5 poststimulation. Despite the proliferation arrest, stimulated T cells successfully differentiated into effector cells, as evidenced by their capacity for proinflammatory cytokine secretion, potent adhesion and cytotoxicity. Prolonged mercaptopurine treatment of mice for 20 weeks selectively reduced the CD4+ memory response to a repeatedly encountered HEL antigen, but did not affect the T cell memory pool to the previously presented OVA antigen. A shorter, 4 weeks, treatment with mercaptopurine did not inhibit the memory response to either antigen.

CONCLUSIONS

T cells arrested from cycling by thiopurines can still differentiate into potent effector cells capable of propagating the inflammatory process. Thiopurine treatment results in depletion of antigen-specific memory T cells, but this effect is dependent upon repeated encounters with the antigen over a prolonged time course.

The frequency of the predominant Jewish mutations in BRCA1 and BRCA2 in unselected Ashkenazi colorectal cancer patients

It is presently unclear whether carriers of BRCA1 mutations have an increased risk for colorectal cancer (CRC). To gain insight into this issue, 225 unselected Ashkenazi Jewish CRC patients were tested for the presence of the three common Jewish BRCA1/2 germline mutations: 185delAG and 5382insC (BRCA1) and 6174delT (BRCA2). A total of four carriers was found (4/225, 1.78%). This frequency is similar to the estimated normal Ashkenazi population frequency, thus suggesting that these specific mutations do not contribute to CRC predisposition.

Alpha interferon has no effect on lidocaine metabolism in the rat

Interferons (IFN) inhibit activity of many isoenzymes of the hepatic microsomal cytochrome P-450 system. This inhibition is species specific. Lidocaine is metabolized by cytochrome P-450 III A 4. We investigated in the rat the effect of rat alpha-IFN on lidocaine elimination and on its extraction by the isolated perfused rat liver. To determine elimination, the femoral artery and vein were cannulated. 24 h later, the conscious rat was given lidocaine through the venous catheter and blood was drawn from the arterial catheter for lidocaine determination every 3 min for 20 min. 7 rats were pre-treated with intramuscular rat alpha-IFN 7.5 x 10(5) U, 24 h prior to the experiment and another 4 rats were given saline i.m. The lidocaine elimination rate constant was unchanged, 0.065 min-1 and 0.063 min-1 for the control and IFN groups, respectively. To investigate lidocaine extraction, the isolated perfused rat liver was used. Perfusate samples from the portal and hepatic veins were drawn at 2 min intervals for 20 min, and lidocaine extraction determined. Extraction was determined in two groups of 6 rats each. The first group served as control and these rats were injected with saline only, while in the second group, the rats were pre-treated with rat alpha-IFN 7.5 x 10(5) U. Lidocaine extraction by the isolated perfused rat liver remained unchanged, 97.0 +/- 0.7% and 94.0 +/- 2.4% in the control and IFN treated groups, respectively. It is concluded that the rat alpha-IFN affects neither the elimination nor the extraction of lidocaine.

A comparison of metronidazole and sulfasalazine in the maintenance of remission in patients with ulcerative colitis

In a double-blind, randomized trial, we tested the effectiveness of metronidazole (0.6 g/day) against sulfasalazine (2 g/day) in the maintenance of remission in patients with ulcerative colitis. The patients were in remission for 1-11 months at entry to trial, which lasted for 12 months. Forty patients entered the trial and 33 completed it. Metronidazole was found to be slightly more effective than sulfasalazine, a difference statistically significant only at 12 months. Six patients also completed a crossover trial. Remission was maintained for 12 months in 3 patients by metronidazole and in none of the 6 by sulfasalazine. No significant side effects were noted, and in particular, no paresthesias were reported. This trial, as well as our previous one, suggests that metronidazole may be useful in the maintenance of remission in patients with ulcerative colitis, but that it is ineffective in the therapy of the acute attack.

Intestinal cancer in patients with Crohn's disease. A population study in central Israel

A population study of Crohn's disease (CD) during the years 1970-1980 was performed in a defined area in central Israel with 1,400,000 inhabitants. Three hundred and sixty-five patients with definite CD were identified, and a complete follow-up was obtained with particular attention to intestinal cancer. The mean follow-up time was 9.95 years (range, 1-49 years). Forty-four per cent of the patients were operated on, but only a few had total colectomy or bypass operations. Only one patient developed colorectal cancer after 7 years of disease. The observed to expected ratio for this cancer was 1.14 at 10 years of disease and 0.73 at 20 years of disease. The incidence of colorectal cancer was not significantly different from the expected in the population. None of the patients developed small-bowel cancer. At least five patients had extraintestinal malignancies. A review of the literature showed conflicting results with regard to cancer risk in CD. The risk was not significantly increased in the two existing population studies, including the present one.