In Murine Disseminated Candidiasis, Serum Amyloid P Component Inhibits Inflammation and C-Reactive Protein...

Candida albicans is a ubiquitous commensal fungus that may be lethal once it gains access to the bloodstream, following a breach in protective barriers such as skin or gut lining. Intravenous injection of C. albicans (4.5 × 10⁴ yeasts/gm of mouse) leads reproducibly to systemic infection with a median survival of about 75 h. We studied the effects of two human innate immune effectors on the course of systemic infections. The soluble human pentraxin serum amyloid P component (hSAP) retards death in murine disseminated candidiasis. In contrast, another soluble pentraxin, human C-reactive protein (hCRP), hastens death. To examine the pathological basis for these differences, necropsies were performed, and the right kidney was removed for study. Candidiasis caused abundant collagen deposition (the precursor to fibrosis) and loss of contrast between the kidney medulla and cortex. Daily administration of subcutaneous hSAP following the intravenous injection of C. albicans preserved the discrete histological difference between cortex and medulla and lessened host collagen deposition. Yeasts and hyphae within abscesses were decorated with hSAP. Contrastingly, kidneys from animals administered C. albicans and hCRP showed extensive collagen deposition and loss of the boundary between the cortex and the medulla of the kidney. hCRP did not bind to fungi but bound to damaged tissue surrounding abscesses, leading to a more destructive infection with loss of tissue. Staining cells with antibodies to CD45 (to detect T-lymphocytes, myelocytes, monocytes, and macrophages) and antibodies to Ly-6G (neutrophils, and granulocytes) showed that hSAP retarded infiltration of inflammatory cells into diseased areas. The results are consistent with the hypothesis that early administration of hSAP represses the migration of inflammatory cells, dampens the production of collagen by fibroblasts, and dampens the overall immune response of the host to infection. In doing so, hSAP prolonged life, whereas hCRP facilitated the infectious process and hastened death.