Anatomical and physiological species-specific differences make cattle more prone to developing respiratory disease than other species. They have a smaller lung capacity, which requires a higher rate of breathing compared to other species. Their lung anatomy is prone to allowing pathogens deeper into in lungs, which have poor collateral ventilation, predisposing cattle to emphysema. The mucociliary escalator provides barrier function in the respiratory tract; it can be disrupted by environmental and microbial factors. The innate immune response in the respiratory tract comprises phagocytic cells, pro-inflammatory cytokines, anti-microbial peptides, and other soluble factors. The adaptive immune response in the respiratory tract is performed by mucosa-associated lymphoid tissue and other secondary lymphoid organs, including tonsils and lymph nodes. Disease-sparing in the respiratory tract is accomplished by local and systemic antibody and cell-mediated immunity (CMI) responses.