Studies on reticulin. I: Serological and immunohistological investigations of the occurrence of collagen type III, fibronectin and the non-collagenous glycoprotein of Pras and Glynn in reticulin.

Collagen Type III, fibronectin and a non-collagenous reticulin component (NCRC) are all secretory products of fibroblasts and other mesenchymal cells. Antisera to human collagen III (isolated from the placenta) human plasma fibronectin, and NCRC (from spleen) have been used to examine possible antigenic relationships between these proteins both by serological studies and by comparison of the distribution of the proteins in various tissues using immunofluorescence. For other comparative purposes, the distribution of collagen and of reticulin in the same tissues was also sought using conventional histological methods. Serologically, the 3 antisera showed distinct specificities. However, when used on sections all 3 antisera gave closely similar staining patterns broadly resembling that of histological "reticulin", although minor differences were noted to be characteristic of the distribution of the respective antigens in certain tissues and in cell monolayers. The results support previous suggestions that histological "reticulin" is not a single entity but is a compound fibrous structure containing collagen Type III, fibronectin and at least 1 additional non-collagenous glycoprotein (NCRC).