Human lymphocyte responses are enhanced by culture at 40 degrees C

In vitro responses of human peripheral blood lymphocytes (PBL) were found to be markedly enhanced by culture at 40 degrees C rather than at the conventional temperature of 37 degrees C. We studied proliferative responses of lymphocytes by activation by phytohemagglutinin (PHA) concanavalin A (Con A), pokeweed mitogen (PWM), and allogeneic lymphocytes in mixed lymphocyte culture (MLC) and found enhancement of DNA synthesis at the higher temperature. Cytotoxic T cell responses to allogeneic cells were also enhanced when MLC was done at 40 degrees C. These enhanced immune responses appear to be due in part to increased numbers of participating cells. If in vitro lymphocyte responses correlate with in vivo responses, then fever associated with infection or tumor may be beneficial whereas that associated with autoimmune disorders may have a detrimental effect.

DNA replication in human lymphocytes during aging

An analysis of the accuracy of protein and DNA synthesis in human lymphocytes with respect to aging has been carried out. The response of human peripheral lymphocytes, from young and old adults, to phytohemagglutinin was measured at varying temperatures. This should provide a sensitive test for the accumulation of altered thermolabile proteins that are rate limiting in the response to phytohemagglutinin. At 37 degrees C the rate of thymidine incorporation as well as the induction of DNA polymerase in phytohemagglutinin-stimulated lymphocytes from old and young adults were similar. Also at elevated temperatures, the thermosensitivity of DNA replication in lymphocytes from young and old adults was the same. DNA polymerase was purified from PHA-stimulated lymphocytes from young and old adults. The fidelity of DNA synthesis using poly (dC) as a template was similar with both enzymes. However, DNA polymerase-alpha purified from old adults was thermolabile compared to the enzyme from young adults. Thus, while the lymphocytes from old individuals may have heat labile proteins, they do not limit their proliferative capacity.

Distribution of albumin variants Naskapi amd Mexico among Aleuts, Frobisher Bay Eskimos, and Micmac, Naskapi, Mohawk, Omaha, and Apache Indians

In order to help define the boundaries of the distribution of the albumin variants Naskapi and Mexico which are polymorphic among several American Indian groups, we examined sera from Micmac, Mohawk, Northwest River Naskapi, Omaha and Apache Indians, and from Aleuts and Eskimos. Sera from a total of 1,524 individuals were examined. Using a cellulose acetate membrane electrophoretic system with Tris-Citric acid at pH 5.4 we were able to distinguish normal albumin and both variants in the same run. Naskapi and Mexico variants were absent from Aleut, Eskimo, Micmac, Mohawk and Omaha samples. The albumin Naskapi variant was present in an allele frequency of 0.03 in the Naskapi Indian sample. Albumin variants Naskapi and Mexico were found in the Apache sample at frequencies of 0.016 and 0.037, respectively. This report supersedes that previously published by Schell and Agarwal ('76). Generally, within an area there is a correspondence between changes in the frequency of albumin variants and changes in the ethnic background and history of the area's populations. At the same time, when viewing widely separated areas, relationships between distant groups based on linguistic and cultural similarities are paralleled on a biologic level by the distribution of normal albumin and variant albumins.

Screening for deficits in DNA repair by the response of irradiated human lymphocytes to phytohemagglutinin

An assay has been developed to measure the ability of human lymphocytes to repair damage to DNA. In this assay, purified human lymphocytes are exposed to graded doses of radiation and then stimulated with phytohemagglutinin to undergo DNA replication. The rate of incorporation of thymidine in irradiated lymphocytes during the second and subsequent rounds of DNA replication is taken to be indicative of the ability of the cells to repair damage to DNA. In lymphocytes from normal individuals, X-irradiation with doses of 100 to 800 rads was found to inhibit phytohemagglutinin-stimulated thymidine incorporation proportionally to the dose of radiation without curtailing the induction of DNA polymerase. The response to phytohemagglutinin of lymphocytes from a patient with xeroderma pigmentosum after exposure to graded doses of X-irradiation was found to be similar to that of the normal controls, whereas the response after ultraviolet irradiation was markedly impaired. In contrast, lymphocytes from patients with ataxia telangiectasia were hypersensitive to X-irradiation. The data on these clinical syndromes support the idea that this assay measures DNA repair and indicates the feasibility of using this method for screening individuals for genetic deficits in DNA repair.

Infidelity of DNA synthesis as related to mutagenesis and carcinogenesis

An assay system has been developed for measuring the fidelity of DNA synthesis in vitro by using synthetic polynucleotide templates and purified DNA polymerases. Nearest-neighbor analysis of the synthesized product indicates that noncomplementary nucleotides are incorporated as single base substitutions. The accuracy of DNA synthesis can be decreased by (1) prior alkylation of the template, (2) increasing the relative concentration of incorrect nucleotides, and (3) addition of specific metal salts to the reaction mixture. As an initial evaluation of the utility of this system, the effects of 31 metal salts on the fidelity of DNA synthesis have been determined. The results indicate that potential metal mutagens and/or carcinogens may be detected by measuring alterations in the fidelity of DNA synthesis.

DNA polymerase activity as an index of lymphocyte stimulation: studies in Down's syndrome

The ability of peripheral blood lymphocytes to respond to phytohemagglutinin (PHA) in vitro was studied in patients with Down's syndrome. The response was measured by the increase in DNA polymerase activity and the rate of incorporation of tritiated thymidine by the cultured lymphocytes. These activities were significantly lower in PHA-stimulated lymphocytes from patients with Down's syndrome compared with age- and sex-matched, mentally retarded patients without Down's syndrome from the same institution and the normal healthy volunteers. The impairment in response to PHA does not seem to be related to the presence of Australia antigen in patients with Down's syndrome or to institutionalization itself. In contrast to DNA polymerase activity and thymidine-(3)H uptake, there was no significant difference in the percentage of blast transformation in the three groups studied. The poor response of the lymphocytes from patients with Down's syndrome to a mitogenic stimulus could reflect an impairment of cellular immune functions in these patients which may be one of the factors contributing to the vulnerability of these patients to repeated or persistent infections.