Ultrastructural and immunohistochemical studies of stromal cells in lamina propria of human fallopian tube ampullar mucosa: the recognition of 'CD34 positive reticular network' and its putative function for immune surveillance.

This paper aims at clarifying the cellular differentiation at the ultrastructural and immunohistochemical levels in normal stromal cells of the fallopian tube ampullar mucosa in order to arrive at a functional interpretation of these cells. Techniques used were histology, histochemistry, transmission and scanning electron microscopy, as well as light and ultrastructural immunohistochemistry for the CD34 antigen. Three types of stromal mesenchymal cell were identified. The most frequent cell-type had a fibroblastic shape and lacked the lamina and myofilaments typical of smooth-muscle. It was, however, positive for alpha-smooth-muscle actin (alpha-SMA). It was negative for desmin (D), but positive for the CD34 antigen. This cell was therefore rather undifferentiated ultrastructurally but had a partial smooth-muscle immunophenotype: it was designated as an ultrastructurally undifferentiated smooth-muscle cell (U-SM cell). A second category consisted of overt smooth-muscle cells (SM cells): they were rich in myofilaments, had a lamina and were D(+) and alpha-SMA(+). The third category resembled SM cells but were D(-): these were designated D(-) SM cells. U-SM cells, SM cells and D(-)SM cells accounted for 83%, 13% and 4% of the total stromal cell population respectively. U-SM cells had lipid-rich residual bodies, solitary cilia, simple intercellular and cell-to-matrix junction, and they were frequently adherent to mononuclear cells. This phenotype was present irrespective of the varied clinical picture of the patients from whom samples were obtained. The observations suggest that the stroma of the fallopian tube ampullar mucosa consists of a reticulum composed largely of CD34(+) U-SM cells in combination with mononuclear cells. One of the main roles suggested for this CD34 positive reticular network is immune surveillance.