Plays a role as inhibitor of T-cells proliferation induced by CD3. Inhibits expression of IL2RA on activated T-cells and secretion of IL2. Inhibits tyrosine kinases that are required for IL2 production and cellular proliferation. Inhibits phospholipase C-gamma-1/PLCG1 phosphorylation and subsequent CD3-induced changes in intracellular free calcium. Prevents nuclear translocation of nuclear factor of activated T-cell to the nucleus. Plays a role in the inhibition of T- cell proliferation via IL10 secretion by cutaneous dendritic cells. May be a marker of CD4(+) CD56(+) leukemic tumor cells. {ECO:0000269|PubMed:11093127, ECO:0000269|PubMed:15737213, ECO:0000269|PubMed:7722299, ECO:0000269|PubMed:9233604, ECO:0000269|PubMed:9389317, ECO:0000269|PubMed:9647226}. This is the function of Ensembl gene identifier ENSG00000134256 (CD101, CD101 molecule).