Cellular immunosenescence: an overview

Recent studies on space flights suggest that certain T cell immunologic activities are vulnerable to microgravitation. It would be desirable to know the extent to which these changes can be prevented or reversed. Since the changes observed are analogous to the effects of aging on immunity, a brief overview is presented of our current knowledge of age-related changes in immune cells and of the various interventional methods which have been used successfully in preventing the decline with age and in elevating the levels of immune functions of old individuals.

Effects of untreated bed nets on the transmission of Plasmodium falciparum, P. vivax and Wuchereria bancrofti in Papua New Guinea

The impact of untreated bed nets on the transmission of human malaria and filariasis in a village in a hyperendemic area of Papua New Guinea was studied. In anopheline mosquitoes, the Plasmodium falciparum sporozoite antigen positivity rate, filarial infection rates and human blood indices dropped significantly after bed nets were introduced. This reduction in human-vector contact did not affect mosquito density as no significant difference in either landing rates or indoor resting catches was found. The number of bed nets in a house and ownership of dogs were factors significantly associated with a reduction in the number of indoor resting mosquitoes. However, the reduction in the P. falciparum sporozoite antigen rate in mosquitoes was not accompanied by a reduction in either malaria parasite or antibody prevalences or titres against the P. falciparum circumsporozoite protein.

Mechanisms of thymic lymphomagenesis by the retrovirus SL3-3

These studies report changes occurring in the thymus of AKR and NFS/N mice after infection with the lymphomagenic retrovirus SL3-3. In virus-infected AKR fetal thymus, the programmed cell death caused by treatment with antibody to CD3 was remarkably diminished. A method of establishing thymic stromal cultures from mice of 1 to 3 wk of age is described. Using this method, it was found that SL3-3 virus infection by neonatal inoculation allowed establishment of thymic stromal cultures from organs removed from AKR mice of 30 to 50 days of age and from lymphomas, whereas thymic stromal cultures could not be established from control mice after 30 days of age. Using NFS/N mice which have no endogenous virus, it was shown that infection of thymic stroma precedes infection of thymocytes and that thymocytes are permissive for infection with SL3-3 virus but not for the nononcogenic retrovirus, Akv, yet Akv virus replicates efficiently in thymic stroma. SL3-3 virus integrates randomly in each lymphoma induced by this virus. The lymphomas are clonal or oligoclonal. Pim-1 and c-myc genes commonly rearranged in other virus-induced thymic lymphoma showed rearrangement in only a few lymphomas. A theory is proposed, based on the work presented here and in recent studies, which states that SL3-3 virus infection of thymic stroma allows infection of thymocyte progenitors entering from the bone marrow. These cells are then altered so that their maturation is delayed and their intrathymic survival is prolonged. This permits virus integration and reintegration that results in the genetic changes which transform the cell.

Alcoholism: a follow-up study of participants in an alcohol treatment programme

One hundred and twelve alcoholic patients treated by an intensive one-month residential programme were followed up for one year. As a group, they were socially disadvantaged and highly dependent on alcohol. Outcome of treatment was assessed at six months and one year following discharge by multiple measures which included assessments of drinking behaviour, measurements of social stability, neuroticism and self-esteem, and self-ratings of satisfaction with important aspects of day-to-day living. During the first six months following treatment, 37% were abstinent or drinking in controlled fashion; during the second six months, 53% achieved this status. Improvement in drinking status was positively related to improvements in all other outcome variables.

Development of lymphoma in the thymus of AKR mice treated with the lymphomagenic virus SL 3-3

A chronological study of the individual thymic lobes of young AKR mice after neonatal inoculation of the oncogenic AKR retrovirus SL 3-3 was performed. 100% of mice treated in this manner develop lymphoma between 60 and 100 days of age. A search for early lymphoma cells in individual thymi was carried out by inoculating the thymocytes subcutaneously in syngeneic and intrathymically in syngeneic and semisyngeneic recipients. Tumor progression was observed in animals between 48 and 60 days of age. These animals have: (a) normal weight lobes, in which no lymphoma cells could be detected, (b) thymus-dependent lymphoma cells, in one or both normal weight lobes; (c) thymus-independent lymphoma cells, found in lobes of normal weight as well as in thymi enlarged by lymphoma cells. Thymocyte characteristics of virus-treated animals of 21 to 63 days of age were compared with those of age-matched controls. Beginning at 28 days a concordant, progressive with time, increase of thymocyte surface staining for the viral envelope glycoprotein gp70 was seen in all lobes from virus-treated animals. Evaluation of cell surface markers by two-color fluorescence with antibodies to CD4 and CD8 showed that after 50 days of age, thymic lobes with and without lymphomas had nonspecific, but marked, alterations of the typical thymocyte surface marker pattern. No characteristic CD4, CD8 surface phenotype was found in primary lymphomas. Using probes for the T-cell receptor J beta 2 gene segments and the Akv ecotropic virus gp70 envelope genes, oligoclonality in J beta 2 rearrangements and clonality using the Akv env genes was demonstrated in thymi with the thymus-dependent phenotype. In lymphomas T-cell receptor beta gene probes showed either oligoclonality or clonality. Clonal virus integrations were found in these lymphomas. These experiments suggest the following series of events in virus-accelerated AKR lymphomagenesis. First, lymphoma cells arise which are initially thymus-dependent and can appear in one or simultaneously in both thymic lobes. These progress to become thymus-independent, fully autonomous, tumor cells. Thymocytes close to or at the time of the initial transformation event show a marked disorder of differentiation defined by the alterations in the CD4, CD8 surface phenotype distribution.

Transcriptional regulation of immunoglobulin heavy chain and T-cell receptor beta chain genes

We have identified factors that bind to functionally important regions in IgH chain promoters and enhancer. One promoter factors is identical to u-EBP-E, an enhancer binding protein. Several promoter-binding proteins are present preferentially in either B cells or fibroblasts although most enhancer-binding proteins have a ubiquitous distribution. Additional characterization of these factors will further our understanding of the mechanisms by which IgH promoters and enhancers interact to achieve B-cell restricted and developmental stage-specific expression of IgH genes. The identification of a TCR beta chain enhancer will allow us to pursue similar questions with respect to the regulated expression this locus.

A transcriptional enhancer 3' of C beta 2 in the T cell receptor beta locus

Run-on transcription experiments were used to demonstrate that transcription of T cell receptor beta chain V genes is activated by DNA rearrangement, in a manner similar to immunoglobulin genes. A transcriptional enhancer likely to be involved in this activation has been identified. A 25-kilobase region from J beta 1 to V beta 14 was tested for enhancer activity by transient transfections, and an enhancer was found 7.5 kilobases 3' of C beta 2. The beta enhancer has low activity relative to the simian virus 40 viral enhancer, does not display a preference for V beta promoters, has a T cell-specific activity, and binds two purified immunoglobulin heavy chain enhancer factors.

Plasmid- and chromosome-coded aerobactin synthesis in enteric bacteria: insertion sequences flank operon in plasmid-mediated systems

Large plasmids were detected in two aerobactin-producing enteric bacterial species (Aerobacter aerogenes 62-I, Salmonella arizona SA1, and S. arizona SL5301) and designated pSMN1, pSMN2, and pSMN3, respectively. Other Salmonella spp., namely, S. arizona SL5302, S. arizona SLS, Salmonella austin, and Salmonella memphis, formed aerobactin but contained no detectable large plasmids. S. arizona SL5283 made no aerobactin. A probe consisting of the aerobactin biosynthetic genes cloned on plasmid pABN5 hybridized to a HindIII digest of pSMN1 but not to digests of pSMN2 or pSMN3. A larger probe, the insert of pABN1 containing the complete aerobactin operon, hybridized to four fragments in HindIII digests of the parent plasmid, pColV-K30. A 2.0-kilobase PvuII fragment responsible for this multiple-hybridization pattern was cloned into vector pUC9 to form pSMN30. The latter was mapped and shown to correspond to either IS1 or to a closely related insertion sequence.

Medical and social factors influencing admission to residential care

The increasing number of people aged over 75 in Britain makes heavy demands on health and social services. To obtain accurate information for rational allocation of resources to domiciliary and residential services a group of 98 housebound women over 75 were compared with a group of 99 women of the same age in residential care. They had a similar range of physical disorders with the exception that deafness was more common among women in residential care. A much higher proportion in residential care were demented. Though in many respects women in residential care had less physical incapacity, a higher proportion needed help at times of crisis. Important social factors were that women at home were more likely to be living with others, and that the principal helper was more likely to be a husband or relative than a neighbour. Both groups received the same amount of support from home helps and community nurses. Any reduction in the number of residential care places for elderly women whose relatives are not available or are unable to cope would require the establishment of an effective community psychogeriatric service and a system for providing appropriate subjects with 24 hour care and supervision.