Elderly high NK responders are characterized by intensive proliferative response to PHA and Con A and optimal health status

Immunomodulating effect of influenza vaccination in the elderly differing in health status

The aim of this study was to analyse whether split influenza vaccine may elicit NK cytotoxic response in the vaccinated elderly people and whether this effect may be maintained over few weeks after vaccination. It was also worth investigating the relation between NK activity in the vaccinated and specific immune protection against influenza and non-specific against other infections. Two groups of volunteers were vaccinated with trivalent split viron influenza vaccine in two consecutive seasons (1999/2000; 2000/2001). The elderly group consisted of 142 people (65-92 years old) in the first season and 110 in the second; while the young (16-44 years old) of 98 and 67 people, respectively. An analysis of NK cytotoxic activity had been done before vaccination, two days, one month and fifth months thereafter. The results revealed that vaccination with the influenza vaccine had an augmenting effect on NK activity, in all groups examined, in both epidemic seasons, visible at two days and 1 month after the vaccination. In the elderly high pre- and post-vaccination NK activity was related to higher titers of anti-hemagglutinin, better health status and lower incidence of all cause respiratory tract infections. At the second vaccination, most of the elderly with chronic medical conditions and high NK activity, who did not attain the protective level of anti-hemagglutinins in the first season, converted into the protected. High pre- and post-vaccination NK activity predisposes elderly people to the protective humoral anti-hemagglutinin response and gives better protection from respiratory tract infections.

Natural killer activity and thyroid hormone levels in young and elderly persons

BACKGROUND

On the basis that (1) multiple interactions exist between the hormonal and immune systems, and (2) aging is accompanied by changes in thyroid hormone metabolism and responsiveness, we postulate that thyroid hormones may be involved in the observed decrease in natural killer (NK) activity in a population of apparently healthy elderly subjects. The purpose of the study is to compare NK cytotoxic activity and serum concentrations of TSH and thyroid hormones in healthy old and young people, and to assess in vitro the effects of triiodothyronine (T(3)) on NK activity.

MATERIALS AND METHODS

Sixteen of the 47 healthy old people (mean age 64 +/- 5.2) were classified as optimally healthy, and the remainder as 'almost healthy' (according to the criteria of the Senieur protocol) [Ligthart et al., Mech Ageing Dev 1984;28:47-55]; the mean age of the healthy young people was 23.3 +/- 2.3 years. NK cytotoxic activity of peripheral blood mononuclear cells was assessed using (51)Cr release from K562 target cells. The cutoff level for defining low and high NK responses was set at a value of 20%. Serum concentrations of TSH, total thyroxine (T(4)) and total triiodothyronine (T(3)) were measured by radioimmunoassay.

RESULTS

NK activity in the 'optimally healthy' elderly was high (mean 41 +/- 12%, SE), whereas 'almost healthy' subjects showed low NK activity (mean 6 +/- 5%). Serum T(4) and TSH levels, but not T(3) concentrations were similar in both the young and old. We observed a significant correlation (r = 0.53, n = 21, p < 0.05) between the serum total T(3) level and the NK activity in the elderly individuals. Under in vitro conditions exogenous T(3) significantly increased NK activity in the elderly subjects who had serum T(3) values at the lower end of the reference range. However, no effect of T(3) on NK activity was observed in peripheral blood mononuclear cells obtained from either old or young individuals who had serum T(3) levels at the midpoint of the range.

CONCLUSION

Decreased serum concentrations of total T(3) may contribute to low NK activity in the 'almost healthy' subgroup of the elderly.