AIDS and programmed cell death

Involvement of granule-mediated apoptosis in the cyclic changes of the normal human endometrium

Our objective is to investigate the involvement of granule-mediated apoptosis in the cyclic changes of the endometrium. We demonstrated the localization of CD56, perforin, granzyme B and caspase-3 in the endometrium by immunohistochemistry. We also confirmed the localization of perforin by immuno-electron microscopy, and demonstrated apoptosis in endometrial glandular cells by TdT-mediated dUTP-biotin nick end labeling (TUNEL) and electron microscopy. Uterine CD56-positive natural killer (NK) cells expressed perforin and granzyme B in its cytoplasm. Uterine NK cells increased significantly in the endometrial stroma during the secretory phase, and peaked during the late secretory phase. These cells started decreasing in number during the menstrual period. In endometrial glandular cells, caspase-3 and TUNEL-positive cells increased significantly from the late secretory phase, with apoptosis reaching a peak during the menstrual period. Using electron microscopy, we observed uterine NK cells with chromatin rich, segmented nuclei and intracytoplasmic granules in the stroma obtained from late secretory phase endometria. These cells extended projections to the lining of endometrial glandular cells and attached to form a cell-to-cell contact. In addition, nuclear chromatin was observed to have already cohered and small cytoplasmic organelles were beginning to disappear, suggesting that these endometrial glandular cells were undergoing apoptosis. Utilizing immuno-electron microscopy, intracytoplasmic granules in uterine NK cells were stained with anti-perforin antibody. The findings of this study suggest that granule-mediated apoptosis in endometrial glandular cells induced by NK cells expressing perforin and granzyme B may be associated with the onset of menstruation.

The epidemiology and transmission of AIDS: a hypothesis linking behavioural and biological determinants to time, person and place

Epidemiologically, the Acquired Immune Deficiency Syndrome, AIDS, is transmitted and distributed in the USA and Europe almost entirely in well-defined subsets of populations engaging in, or subjected to, the effects of behaviours which carry high risks of genital and systemic infections. The persons predominantly affected are those engaging in promiscuous homosexual and bisexual activity, regular use of addictive drugs, and their sexual and recreational partners. In such persons and in subsets of populations with corresponding life-styles, the risk of AIDS increases by orders of magnitude. Because of continuity of risk behaviour and of associated indicator infections, the incidence of AIDS over 3-5 year periods is predictable to within 10% of actual totals of registered cases in the USA and UK. Secondary transmission of AIDS beyond these groups is minimal or, in many locations, absent. There is no indication of appreciable spread by heterosexual transmission to the general population. The Human Immunodeficiency Virus, HIV, is transmissible to some extent in general populations, and more so among promiscuous persons. It may cause viraemia, lymphadenopathy and latent infection (HIV disease) in anyone. In persons engaging in risk behaviours which themselves alter or suppress immune responses, it can interact with MHC, antibodies to other organisms and to semen, and other allogenic antigens to initiate a programmed death of CD4 lymphocytes and other defensive cells, as in graft-host rejections. This occurs also in haemophiliacs receiving transfusions of blood products, and is more pronounced in persons with reactive HLA haplotypes. The susceptibility of particular subsets of populations to AIDS is thereby largely explained. But these changes occur in the absence of HIV, and so do Kaposi's sarcoma, lymphadenopathies and opportunistic infections which are regarded as main indicators of AIDS. The hypothesis that HIV-1 can do all this by itself and thereby cause AIDS is falsifiable on biological as well as epidemiological grounds. An alternative hypothesis is proposed, linking the incidence of AIDS to the evolution of contemporary risk behaviour in particular communities and locations in the USA, UK and probably in most of Europe. It does not pretend to explain the reported incidence of AIDS in Africa and other developing regions where data are insufficient to provide validation of the pattern of disease and contributory variables. The immediate, practical implication of this alternative hypothesis is that existing programmes for the control of AIDS are wrongly orientated, extremely wasteful of effort and expenditure, and in some respects harmful.

AIDS as immune system activation. Key questions that remain

Immune system activation is gaining attention as a central part of HIV pathogenesis. Although there is no consensus yet as to the source of the signal or the result of the signalling, this line of thinking represents a significant shift in the paradigm away from considering HIV disease like any other cytopathic viral infection. Hopefully, completion of studies focussed on this approach will lead to more complete understanding of AIDS and more effective therapies, and will at least bring to the fore some of the central unanswered questions in modern cellular immunology.