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Activation-induced cell death is a general mechanism of immune homeostasis through negative regulation of clonal expansion of activated immune cells. This mechanism is involved in the maintenance of self- and transplant tolerance through polarization of the immune responses. The Fas/Fas-ligand interaction is a major common executioner of apoptosis in lymphocytes, with a dual role in regulatory T cell (Treg) function: Treg cell homeostasis and Treg cell-mediated suppression. Sensitivity to apoptosis and the patterns of Treg-cell death are of outmost importance in immune homeostasis that affects the equilibrium between cytolytic and suppressor forces in activation and termination of immune activity. Naive innate (naturally occurring) Treg cells present variable sensitivities to apoptosis, related to their turnover rates in tissue under steady state conditions. Following activation, Treg cells are less sensitive to apoptosis than cytotoxic effector subsets. Their susceptibility to apoptosis is influenced by cytokines within the inflammatory environment (primarily interleukin-2), the mode of antigenic stimulation and the proliferation rates. Here, we attempt to resolve some controversies surrounding the sensitivity of Treg cells to apoptosis under various experimental conditions, to delineate the function of cell death in regulation of immunity.

A large body of evidence on the activity of regulatory T (Treg) cells was gathered during the last decade, and a similar number of reviews and opinion papers attempted to integrate the experimental findings. The abundant literature clearly delineates an exciting area of research but also underlines some major controversies. A linear cause-result interpretation of experimental maneuvers often ignores the fact that the activity of Treg cells is orchestrated with the effector T (Teff) cells within an intricate network of physiological immune homeostasis. Every modulation of the activity of the effector (cytotoxic) immune system revolves to affect the activity of regulatory (suppressive) cells through elaborate feedback loops of negative and positive regulation. The lack of IL-2 production by innate Treg cells makes this cytokine a prime coupler of the effector and suppressive mechanisms. Here we attempt to integrate evidence that delineates the involvement of IL-2 in primary and secondary feedback loops that regulate the activity of suppressive cells within the elaborate network of physiological immune homeostasis.

Background: A new mutation, I1307K, recently was reported in the adenomatous polyposis coli (APC) gene. This mutation was found to be predominant in Ashkenazi Jews, creating a hypermutable area and predisposing the development of carcinoma. The objective of the current study was to estimate the prevalence of this mutation in several of the ethnic groups that comprise the Israeli population and to elucidate the clinical features of the mutation carriers with colorectal carcinoma (CRC)., Methods: A total of 111 consecutive CRC patients were evaluated and their medical history and clinical data recorded. The general population (298 Ashkenazim and 189 Yemenites) also was tested for the presence of this mutation. Mutation screening was performed using both the polymerase chain reaction-based amplification refractory mutation system and a commercial APC kit., Results: Of the total of 111 CRC patients, 15 (13.5%) carried the I1307K mutation and 26 of 487 subjects from the general population (5.3%) carried the I1307K mutation (P = 0.004). Among the 71 Ashkenazi CRC patients there were 12 carriers (16.9%) whereas 17 of the 298 Ashkenazi Jewish general population (5.7%) carried the mutation (P = 0.004). Of the 4 CRC patients of Yemenite origin, 3 carried the mutation and 9 carriers were found among 189 subjects in the general Yemenite population (4.7%) (P = 0.0007). None of the 34 Sepharadic or 2 Arab CRC patients carried the APC I1307K allele. Late age at diagnosis (64.6 years +/- 10.0, which is similar to that of the noncarriers), mostly right-sided tumors, and moderate to good differentiation constituted the phenotype of the mutation carriers., Conclusions: The authors believe the findings of the current study broaden the known spectrum of ethnic groups in which the APC I1307K mutation is prevalent. The phenotype of the mutation carrier CRC patients does not conform to the expected familial pattern of germline mutations. The phenotype and the differential incidence rate of CRC among APC I1307K carriers of various ethnic groups suggest low penetrance., (Copyright 2000 American Cancer Society.)

Fetoscopy and fetal blood sampling were performed in an attempt at prenatal monitoring of a pregnancy at risk for infantile hereditary agranulocytosis (Kostmann's disease). In smears of fetal blood three segmented neutrophils were found out of 200 nucleated cells (1 1/2 per cent). Their presence, although in a lower percentage than in six age-matched controls, was considered to indicate that the fetus was not affected. The newborn infant has developed normally and at the age of four months has a normal number of segmented neutrophils in his peripheral blood. Feasibility of prenatal diagnosis of infantile hereditary agranulocytosis is discussed.

A case is described of antenatal detection of a placental mass by ultrasound in a patient with hydramnios due to chorioangioma and who had a sinusoidal-like pattern and positive oxytocin challenge test (OCT). The importance of frequent fetal heart rate monitoring in cases of suspected chorioangioma is emphasized.