Plasma cells in the bronchoalveolar lavage fluid of a patient with eosinophilic pneumonia. Morphologic proof of local production of antibodies.

We describe a case of eosinophilic pneumonia in which plasma cells appeared in bronchoalveolar lavage fluid (BALF). A 49-year-old man presented with wheezing, lung infiltrates, peripheral eosinophilia, and extremely high IgE levels in serum and BALF. A differential count of BALF revealed 56.6 percent lymphocytes and 1.3 percent plasma cells. The appearance of plasma cells suggests local maturation of B cells and represents a morphologic proof of local production of immunoglobulins. The increased number of lymphocytes suggests their role in B cell differentiation via the lymphokine network.