Common variable immunodeficiency in miniature dachshunds affected with Pneumonocystis carinii pneumonia.

Seven miniature dachshunds, all under the age of 1 year, were presented with polypnea, tachypnea, and exercise intolerance as a result of Pneumocystis carinii pneumonia, which was diagnosed on transtracheal aspirate cytology. In all of the dogs, historical and clinical signs were suggestive of immune incompetence. Immunological studies undertaken were leukogram parameters, serum immunoglobulin fraction quantification, lymphocyte transformation assay. CD3 and CD79a lymphocyte markers on lymphoid tissue, and anti-canine immunoglobulin G immunoperoxidase staining. The immunological studies showed hypogammaglobulinemia, deficiency of serum immunoglobulins A, G, and M, decreased lymphocyte transformation response to phytohemagglutinin and pokeweed mitogens and absence of B lymphocytes with presence of T lymphocytes in the lymphoid tissue stained with CD3 and CD79a lymphocyte markers. The preceding findings suggest that P. carinii pneumonia occurring in the miniature dachshund is a result of both a T- and B-cell deficiency. This presentation is not the classic primary severe combined immunodeficiency syndrome but rather combined variable immunodeficiency, which has been well documented in humans but never in the dog.