Immune profiling of the buffalo mammary gland across graded low somatic cell counts under tropical conditions.

Milk somatic cell count (SCC) indicates udder health and milk quality, but levels much lower than the normal range may signal mammary gland immunocompromise. This study evaluated the immunological status of the buffalo mammary gland across graded low SCC levels under non-infectious conditions (<2 ×10⁵ cells/mL). Forty-eight clinically healthy Murrah buffaloes in early lactation were categorized into four SCC groups: Group 1 (0.20-0.60 ×10⁵ cells/mL), Group 2 (0.61-0.90 ×10⁵ cells/mL), Group 3 (0.91-1.40 ×10⁵ cells/mL), and Group 4 (1.41-1.90 ×10⁵ cells/mL). Buffaloes were screened using the California mastitis test (CMT) and infrared thermography (IRT) to eliminate subclinical mastitis (SCM). Immunological assessments included milk differential leukocyte counts (DLC), phagocytic activity (PA) of neutrophils and macrophages, lymphocyte proliferation response (LPR), cytokine concentrations (IL-2, IL-6, IL-8, TNF-α, IL-10), and milk cortisol levels. Buffaloes having low SCC showed predominant lymphocytes along with significantly (p < 0.05) higher PA and T-cell proliferation, indicating strong mammary immune competence. With increasing SCC, neutrophil proportion and pro-inflammatory cytokines (IL-2 and TNF-α) increased significantly (p < 0.05). However, IL-10 and cortisol remained consistent across all groups. IRT imaging showed uniform udder temperature, indicating no inflammation. The findings show that very low SCC in buffalo milk reflects immune balance, not immunosuppression, due to effective leukocyte function and cytokine regulation.