Employing fluorescent antibodies for the detection of homologous plasma proteins in tissue sections, the distribution of plasma albumin, γ-globulin, ß-lipoprotein, ß1-metal-combining globulin, and fibrinogen has been studied in the tissues of infants and children. Plasma albumin, γ-globulin, and ß1-metal-combining globulin were found in many cells and particularly cell nuclei, connective tissues and interstitial spaces, lymphatics, and blood vessels. ß-Lipoprotein was found mostly in the nuclei of all cell types while fibrinogen was restricted largely to the lymphatic and vascular channels, connective tissues and the interstitial spaces.
The widespread distribution of these plasma proteins in cells and connective tissues indicates the magnitude of the extravascular plasma protein pool which is in equilibrium with circulating plasma. Unfortunately, these results do not permit accurate localization of the sites of production of these plasma proteins, but do give some idea of their intimate relationship to the tissues.