The allelic expression of mouse IL-2 cannot be definitely extrapolated to w
hat might happen in humans. Therefore, we investigated the regulation of al
lelic expression of the IL-2 gene in non-genetically manipulated human T ly
mphocytes by following natural allelic polymorphisms. We found a phenotypic
ally silent punctual change in the human IL-2 at position 114 after the fir
st nucleotide of the initiation codon, which represents a dimorphic polymor
phism at the first exon of the IL-2 gene. This allowed the study by single-
cell PCR of the regulation of the human IL-2 allelic expression in heterozy
gous CD4(+) T cells, which was found to be tightly controlled monoallelical
ly. These findings may be used as a suitable marker for monitoring the IL-2
allelic contribution to effector activities and in immune responses agains
t different infections or in pathological situations.