Human tonsillar T lymphocytes: an immature or activated T-lymphocyte population

In this study we compare the phenotype and the enzyme content of T lymphocytes purified from tonsils and from circulating blood before and different times after in vitro activation with PHA. The phenotype was studied with the following panel of monoclonal antibodies for the presence of activation antigens: OKT9, OKT10, anti-Dr, and Tac antigen. The enzyme content was studied by estimation of the LDH isoenzyme distribution and the enzymes of the purine metabolism ADA and PNP. In addition, the in vitro responsiveness of the T lymphocytes from tonsils and blood to human recombinant interleukin 2, to the lectins PHA, Con A and PWM was also studied. The LDH isoenzyme pattern expressed as B:A ratio decreases progressively after in vitro activation of T lymphocytes. The B:A ratio is already significantly different as early as 12 hr after activation, at a time that OKT9 and Tac are already expressed, but before the expression of OKT10, HLA-Dr, and the onset of the DNA synthesis. Tonsillar T lymphocytes exhibit also a significantly lower B:A ratio, but the activation antigens are not detected on their surface, except for the Tac antigens by means of a sensitive protein A rosette assay. Tonsillar T lymphocytes have a better responsiveness to lectins and recombinant II-2 than the corresponding circulating T lymphocytes. Therefore we are in favor of the hypothesis that tonsillar T lymphocytes contain activated T lymphocytes.