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. Author manuscript; available in PMC: 2011 May 1.
Published in final edited form as: Clin Immunol. 2010 Mar 25;135(2):223–235. doi: 10.1016/j.clim.2010.02.017

Figure 2. Disorders of homeostasis.

Figure 2

Surfactant homeostasis is achieved by the balanced production of surfactant in AEC-II and its recycling or catabolism in AEC-II and catabolism in alveolar macrophages. The PAP syndrome, characterized by accumulation of surfactant, can occur with disruption of GM-CSF signaling at the level of GM-CSF production as in GM-CSF deficiency in mice, or the presence of neutralizing GM-CSF autoantibodies in patients with autoimmune PAP, the homozygous presence of genetic mutations in either GM-CSF receptor α or β chains that disrupt GM-CSF signaling. In secondary PAP, the syndrome is presumed to be caused by a reduction in either the numbers or functions of alveolar macrophages caused by any one of various underlying clinical disorders. In contrast, disorders of surfactant production caused by mutations in the genes encoding SP-B, SP-C, and ABCA3 (and likely others) result in the production of biochemically and functionally abnormal surfactant that disrupts alveolar structure resulting in gross parenchymal lung distortion. See text for details.