The proportion of circulating gamma delta T cells increases after the first week of onset of tularaemia and remains elevated for more than a year

In various human intracellular bacterial diseases, an increase of the propo rtion of circulating V gamma 9V delta 2 T cells has been observed. The prev alence of the finding among infected subjects and the time course of the el evation remain to be investigated. In the present study, comprising blood s amples from a large number of cases of ulceroglandular tularaemia, the perc entage of V gamma 9V delta 2 T cells within the first week of onset of dise ase (5.3 +/- 0.7% (mean +/- s.e.m.)) did not differ from that of control su bjects (5.3 +/- 0.8%). Thereafter, percentages increased rapidly and within the interval of 8-40 days mean levels were > 20% (P < 0.001). Of 45 indivi duals sampled within 3 months of onset, 42 showed a percentage of V gamma 9 V delta 2 T cells of > 10%. Significantly increased levels were still recor ded at 18 months (13.8 +/- 2.4%; P < 0.05) but not at 24 months (10.2 +/- 2 .1%; P > 0.10). Thus, a consistent increase of circulating V gamma 9V delta 2 T cells was demonstrated in tularaemia. The initial delay and the prolon ged course of elevation may suggest a role in immunoregulation and/or immun ological memory. Furthermore, the percentage of gamma delta T cells express ing tumour necrosis factor-alpha in response to phorbol myristate acetate w as decreased during the first week and up to 40 days after onset, possibly reflecting the modulation of an inflammatory response.