The prolactin inducible protein/gross cystic disease fluid protein-15 deficient mice develop anomalies in lymphoid organs.

The Prolactin Inducible Protein (PIP) is a 15 kDa protein secreted by normal apocrine glands, including salivary, lacrimal and sweat glands. PIP levels are normally low in the mammary glands of healthy individuals, but high levels have been observed in pathological conditions of the breast such as benign breast cystic disease and breast cancer. While the function of PIP is not well elucidated, accumulating evidence strongly point to a role in both innate and adaptive immunity. Using PIP deficient mice (Pip-/- mice) our laboratory demonstrated that loss of PIP function led to impaired T helper type 1 response and cell mediated immunity. In the present study we provide additional supporting evidence showing abnormal lymphocytic distribution in primary and secondary lymphoid organs of Pip-/- mice. Significant morphological changes in the Eustachian tube, an immune-protected site where PIP is normally found, were also associated with the absence of PIP. Collectively, these results further support an immuno-regulatory role for PIP and have implications for a spectrum of immune-related illnesses including otitis media and hearing loss as well as breast cancer.