Age and sex differences in immunocompetence

The probable role of an immunological component in ageing and senescence has attracted the attention of biologists, immunologists and gerontologists. Immune competence declines as man and experimental animals grow old. While lymphoid organs may be expected to 'age' along with other tissues, the possibility exists that lymphoid failure of itself accelerates senescence by predisposing individuals to infection and degenerative diseases. There is now enough evidence to differentiate effects that are due to age per se from other causes. Also, evidence of a greater female than male immunologic responsiveness is ample, but hypotheses to explain these observations are only partially adequate. This review attempts to summarise our knowledge of the effects of age and sex on immunocompetence with the aim of discussing the theories put forward to explain our observations.