A Unique Vγ5-T-cell population in the murine mammary gland

Mammary epithelia and the epidermis share a common embryologic origin. Like resident epidermal T cells (ETC), a significant number of murine mammary gland T cells (MTC) express Vγ5-T-cell receptors (TCR). MTC were assessed to see if they express the same invariant Vγ5/Vδ1-TCRs as those of ETC. MTC-derived hybridomas, positive for Vγ5-TCRs, expressed Vδ5 instead of Vδ1. Additionally, they showed non-germline additions in the γ-TCR and δ-TCR junctions, sharing among them an identical 19-nucleotide N-region in the δ-TCR junctions. Vγ5-TCR and Vδ5-TCR gene sequences from fresh peripartum MTC also contained variable N-regions, including a 7-nucleotide N-region similar to one found in the hybridomas. Thus, Vγ5-TCR+ MTC are distinct from Vγ5-TCR+ ETC by expressing variable non-canonical TCRs, predicting differences in the two T-cell populations in ligand specificity and in function.