A unique Vgamma5-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 Vgamma5-T-cell receptors (TCR). MTC were assessed to see if they express the same invariant Vgamma5/Vdelta1-TCRs as those of ETC. MTC-derived hybridomas, positive for Vgamma5-TCRs, expressed Vdelta5 instead of Vdelta1. Additionally, they showed non-germline additions in the gamma-TCR and delta-TCR junctions, sharing among them an identical 19-nucleotide N-region in the delta-TCR junctions. Vgamma5-TCR and Vdelta5-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, Vgamma5-TCR+ MTC are distinct from Vgamma5-TCR+ ETC by expressing variable non-canonical TCRs, predicting differences in the two T-cell populations in ligand specificity and in function.