The Australian journal of experimental biology and medical science最新文献

While the virgin AFC-progenitors for an adoptive immune response in neonatal germ-free CBA mouse spleen are small, dense cells, the equivalent cells in the adult are a larger, lighter density population. The effects of injections of unrelated antigens on the physical properties of the AFC-progenitors in neonatal spleen were investigated to test the postulate that the physically distinct "virgin" AFC-progenitors in the adult arose by a process of non-specific activation. Spleen cells from 7-day-old germ-free CBA mice were separated by sedimentation at unit gravity or by density on continuous albumin gradients, and the fractions were tested for NIP-specific AFC-progenitor activity using an adoptive immune assay which gave a direct linear measure of B cell activity. If the donor neonatal animals were injected one day previously with POL or PPD, the NIP-specific AFC-progenitor activity shifted from the typical small, dense lymphocytes to larger, lighter cells. The physical properties of these stimulated AFC-progenitors resembled those of IgM AFC-progenitors in normal adult mice. These results experimentally confirm the theory that environmental stimuli induce a non-specific "activation" of a particular subset of "virgin" B cells.

A preliminary study of acidic alpha-glucosidase in a variety of tissues was carried out in an attempt to develop a test which might be used to detect individuals heterozygous for the genetype associated with generalized glycogenosis in beef Shorthorn cattle. Of the tissues readily available peripheral lymphocytes were chosen as being likely to be the most suitable. It was concluded that, when coupled with genealogical information, assays of alpha-glucosidase in extracts of lymphocytes were useful for identifying heterozygous individuals with a reasonably high degree of probability.

Daily administration of increasing doses intraperitoneally of 2.5-4.0 mg NaCN/kg to male Wistar rats for 5 weeks produced acute signs of poisoning immediately post-injection but no sign of chronic toxicity except lower final body weights than in control rats. CN-treated rats had less liver copper than controls, but not below the range of normality, and their liver mitochondrial membranes were 24% less able to bind adenine nucleotides than control membranes. No other biochemical or pathological sign of copper deficiency occurred. Liver cytochrome oxidase activity was normal after the 5 weeks of CN-administration, as was the ability of liver mitochondria to synthesize phospholipids. The ultrastructure of hepatocytes was normal without evidence of the enlarged, misshapen mitochondria produced by copper deficiency. Normal cytochrome oxidase activity of liver mitochondria, together with reduced liver copper levels and reduced binding affinity of mitochondrial membranes for adenine nucleotides, indicate that the membrane binding site for adenine nucleotides is not cytochrome oxidase per se but may involve copper, perhaps by virtue of its cationicity. With repeated exposure to CN- rats develop tolerance to acute poisoning. It is suggested that this may be due to the switch in glucose catabolism towards the pentose pathway at the expense of other pathways.

An in vitro culture method was used to study secondary cell-mediated responses to ectromelia virus infection in mice. Infected, syngeneic spleen cells or peritoneal cells were efficient "stimulator" cells when cultured with "responder" cells obtained from mice infected with ectromelia 4-6 weeks previously. The kinetics of generation of cytotoxic cells in cultures were determined; a peak occurred on days 4-5. A separation procedure performed on the cytotoxic cells showed that activity was associated mainly with the Ig-negative subpopulation (T cell-rich) and that H-2 compatibility between cytotoxic cells and target cells was required. The secondary response was virus-specific, at the level of both induction and target cell lysis, at least so far as ectromelia and lymphocytic choriomeningitis (LCM) viruses are concerned. Seperation of responder cells prior to culture showed that a potent secondary response was generated with the Ig-negative (T cell-rich) subpopulation and only a weak response was observed when the responder cells were Ig-positive (rich in B cells). Infected stimulator cells did not appear to secrete significant amounts of soluble antigen into the medium over 4 days of culture. Thus, antigenic patterns effective in memory T cell stimulation may be largely associated with the surfaces of infected cells.Pretreatment of ectromelia virus with UV- or gamma-irradiation did not impair its ability to induce antigenic changes in stimulator cells. Stimulator cells treated with UV-or gamma-irradiated virus for 1 h and then immediately with pactamycin to inhibit further viral protein synthesis and replication were efficient stimulators, thus indicating that antigenic changes are induced very rapidly on the surface of stimulator cells after uptake of virus. These treatments are being used to further characterize the cellular requirements in the stimulator population.

Equilibrium density separation on continuous albumin gradients was used to separate and characterise the T cells responding by proliferation to both syngeneic and allogeneic stimulating cells in the one-way mixed leucocyte reactions (MLR). In CBA mouse spleen both light and dense T cells were capable of responding in an allogeneic MLR. No T cells responding to stimulation be syngeneic B lymphocytes could be isolated from adult or 7-day CBA mouse spleen. In adult CBA mouse thymus, cells responding to allogeneic stimuli were enriched in the light density region, along with the low theta subpopulation. Self-reactive cells, responding with proliferation when cultured with syngeneic adult CBA splenic lymphocytes, and found in adult and 4-day CBA mouse thymus, were also enriched in the light density zones. However, in adult thymus syngeneic MLR reactivity was also found in the dense zones, and the density distribution profiles of total syngeneic MLR responding cells revealed a series of peaks extending over the whole density range. It was suggested that these syngeneic MLR responders undergo a complete maturation process, including progressive density increases, within the thymus gland. Such a sterile differentiation pathway could be a censorship process, leading to death of self-reactive cells within the thymus.