Developmental changes of double-negative (CD3+ 4-8-) T cells in human peripheral blood

The frequency of double-negative (CD3+4-8-) T cells in the circulating pool was examined for different age groups. Adult peripheral blood contained a substantial but variable proportion of double-negative T cells. Double-negative T cells in adult peripheral blood were shown to lack the alpha/beta heterodimers of the T cell antigen receptor (TCR alpha/beta) but express the gamma chain of the TCR (TCR gamma), when examined using the corresponding monoclonal antibodies. In contrast to adult blood, double-negative, TCR alpha/beta-negative, and TCR gamma-positive T cells were very scarcely demonstrated in the cord blood of newborn infants. It was found that the percentages of double-negative T cells correlated very well with those of TCR alpha/beta negative T cells. These double-negative T cells in the peripheral blood gradually increased with advancing age and reached in frequency the adult level around one year of age. The results suggested that double-negative T cells expressing the TCR gamma/delta might play an ontogenically unique role in the development of the T cell functions.