Influence of the thymus and the normal microflora on the plasma fibronectin concentration in mice.

The plasma fibronectin (pFN) concentration (cc) of untreated genetically or artificially athymic mice, or treated with TP-4 (thymus hormone sequence analog synthetic preparation) showed no significant difference from their euthymic or untreated controls. In contrast, the pFN cc in mice with different microbiological state showed significant alterations; the highest level occurred in conventional mice and the lower level in germfree mice was increased by bacterial monocontamination. The alternation from SPF into conventional state in nude mice also resulted in the increase of the pFN cc. Based on these and earlier results, it was assumed that the pFN cc is independent from the presence or absence of the thymus, but it depends on the actual microbiological state of the macroorganism.