The most abundant cell type in lung interstitium is fibroblasts. They resemble ordinary fibroblasts but have some distinguishing features, for example, they have long branching processes and gap junctions. Their principle function is production of type III collagen, elastin, and proteoglycans of the extracellular matrix of the alveolar septa. Pulmonary fibroblasts (PF) play an important role in the repair and remodeling processes following injury. The controlled accumulation of fibroblasts to sites of inflammation is crucial to effective tissue repair after injury. Either inadequate or excessive accumulation of fibroblasts could result in abnormal tissue function. For example, the excess proliferation of fibroblasts contributes to the adventitial thickening observed during the development of hypoxia-induced pulmonary hypertension. HPF from AcceGen Biotech Research Laboratories are isolated from human lung tissue. HPF are cryopreserved at primary culture and delivered frozen. Each vial contains >5 x 10^5 cells in 1 ml volume. HPF are characterized by immunofluorescent method with antibody to fibronectin. HPF are negative for HIV-1, HBV, HCV, mycoplasma, bacteria, yeast and fungi. HPF are guaranteed to further expand for 15 population doublings at the condition provided by AcceGen Biotech Research Laboratories.