Respiratory diseases continue to be a major cause of clinical manifestation, mortality, production loss, and reduced carcass quality. Given the overlapping clinical manifestations of various causes of bovine respiratory disease (BRD), it is often necessary to conduct pathologic and laboratory investigations to confirm a specific diagnosis in complicated cases. A specific diagnosis is useful to direct antimicrobial or anthelmintic therapy, vaccination programs, and biosecurity practices. Fifty-four lung specimens were collected from adult bulls from Dronka Abattoir, Assiut, Egypt to study the pathological and immunohistochemical alterations of the lung tissue and focus on their relation to the immune cells. Four different forms of lung affections were common; chronic catarrhal pneumonia (fibrosis and hyperplasia with moderate cellular inflammatory cells), chronic interstitial pneumonia (diffuse thickening of the interstitium due to fibrosis, increased cellularity and smooth musculature), pulmonary emphysema (rupture of alveolar walls with communication of alveolar spaces and the appearance of aerated lung tissue) and fibrinous pneumonia (fibrinous exudate with erythrocytic aggregation in the alveoli and bronchiole). In this study, we used a new approach for diagnosing lung affections; CD3-T lymphocytes. CD3-positive T-lymphocytes were in close contact with different pneumonic forms, rather than pulmonary emphysema. The values registered were 13.7, 10.43, 8.40, and 5.19 in chronic catarrhal pneumonia, chronic interstitial pneumonia, fibrinous pneumonia and pulmonary emphysema, respectively. Furthermore, CD3-immunoreactivity is a good marker to recognize different stages of pneumonia. In conclusion, CD3-T lymphocytes could be a beneficial tool for the confirmation of different types of pulmonary pneumonia.