In tuberculous pleural effusion, the initial pleural fluid predominantly contains a high neutrophil count due to the acute inflammatory response to Mycobacterium tuberculosis. Over time, this shifts to a lymphocyte-predominant effusion as the immune response matures. The early neutrophilic dominance is a key diagnostic feature distinguishing it from other chronic causes of lymphocyte-rich effusions. Recognizing this phase helps in early diagnosis and timely management.

Reference: Harrison's Principles of Internal Medicine, Jameson et al, 20th Edition.