Expression of nerve growth factor receptor immunoreactivity on follicular dendritic cells from human mucosa associated lymphoid tissues

Nerve growth factor (NGF) was originally considered as a trophic factor for peripheral sympathetic and sensory neurones; however, recent reports indicate that NGF may induce proliferation of immune and haematopoietic cells. Histochemical studies conducted in human spleen and lymph nodes have suggested the presence of NGF receptor (NGF-R) immunoreactive elements in secondary follicles; however the nature of the cells bearing the NGF-R in lymphoid tissue has not been determined. In this paper we report the results of an immunohistochemical study conducted on mucosa associated lymphoid tissue. Using a specific monoclonal antibody to human NGF-R (mAb 20.4) we observed an NGF-R-immunoreactive population in all secondary lymphoid follicles examined. Double immunostaining revealed that this population was composed of follicular dendritic cells (FDC); lymphoid cells within the germinal centres did not appear to be 20.4 immunoreactive. Cell suspensions from tonsillar follicles also contained NGF-R immunopositive dendritic cells which were enriched by a 20.4 labelled magnetic bead procedure, revealing cells with the morphological characteristics of FDC. Mononuclear cells from human peripheral blood did not contain any NGF-R-immunoreactive elements using our techniques.