新里 昌功

We previously observed Langerhans cells (LC) in the squamous metaplastic urinary bladder in rats fed a vitamin A-deficient diet. Here we report the finding of LC in the iliac lymph nodes, one of the abdominal lymph nodes draining to the urinary bladder. LC had previously only been observed in the superficial and hilar lymph nodes, but never in the abdominal lymph nodes. This is also the first observation of Birbeck granule (BG)-positive LC in the iliac lymph nodes. LC were not found in the transitional mucosa of the urinary bladder. In the present experiments, the LC were observed in both the squamous metaplastic mucosa and lamina propria of the urinary bladder, and also in the iliac lymph nodes, which drain into the urinary bladder. BG-positive LC may mature not only in the squamous epithelia, but also in squamous metaplastic mucosa. LC in the lamina propria of the urinary bladder might migrate to the iliac lymph nodes, which are regional lymph nodes, where they could function in antigen presentation. LC in the skin play a role in antigen-antibody interactions, and the squamous metaplastic mucosa of the urinary bladder may be a similar environment, in which LC in the mucosa can migrate to the regional lymph nodes.

Langerhans cells (LCs) in the squamous metaplastic epithelium of the trachea and the urinary bladder of vitamin A-deficient rats were examined. Both round, immature cells which were considered to be precursor LCs, and mature LCs with prominent dendritic processes, were recognized in the present study. Both cells were positive for anti-protein kinase type II antibody (PKC-II), and although the former did not have Birbeck granules (BGs), the latter did. The precursor LCs without BGs first appeared in the early stage of squamous metaplasia. As the differentiation of squamous metaplasia progressed, the number of BG bearing LCs increased, and the precursor cells became mature LCs in the later stage of squamous metaplasia of both the trachea and the urinary bladder. In the later stage of squamous metaplasia of the urinary bladder, LCs with BGs also appeared in the lamina propria. These findings indicate that precursor cells which probably migrate from the bone marrow, disperse into the metaplastic squamous epithelium in morphologically immature forms, and mature into BG bearing LCs as a result of contact with squamous epithelium.