Subpopulation analysis of human granular lymphocytes: Associations with age, gender and cytotoxic activity

Levels of human blood granular lymphocyte subpopulations were enumerated in 105 healthy donors ranging from 0 to 79 years. Using double-label immunofluorescence, subpopulations of granular lymphocytes were enumerated as follows: Leu7⁺Leu2⁺, Leu7+Leu3⁺, Leu7⁺11^-, Leu7⁺Leu11⁺ and Leu7^-Leu11⁺. The proportion of cells with granular lymphocyte morphology was determined by Giemsa staining. Natural killer (NK) cell activity against K-562 cells and lymphokine-activated killer activity against non-cultured melanoma cells were examined in parallel. Levels of total Leu7⁺ and Leu11⁺ cells increased with age (p=0.0001) and were higher in males than females (p=0.001). The total number of cells with granular lymphocyte morphology had an age-related increase (p=0.0001), but were not significantly higher in males than in females (p=0.07). There was no selective increase in one granular lymphocyte subpopulation versus another since the Leu7⁺11^- (p=0.0001), the Leu7⁺Leu11⁺ (p=0.0001), the Leu7⁺Leu2⁺ (p=0.0001) and Leu7⁺Leu3⁺ (p=0.0004) all had similar age-related increases. The one exception was the Leu7^-Leu11⁺ (p=0.1) granular lymphocyte subset which was low in the first decade of life but had reached maximum levels in the second decade. NK cell activity against K-562 cells was moderately increased with age (p=0.06) with males and females exhibiting comparable activity. In contrast, lymphokine-activated killer cytotoxicity of non-cultured melanoma cells was similar in all age groups. NK cell activity was highly correlated with levels of morphologically defined granular lymphocytes (p=0.005) and moderately with total Leu11⁺ cells (p=0.06) but not with other subpopulations of granular lymphocytes.