摘要：

The localization of antigen in primary follicles and germinal centers of rat popliteal lymph nodes described previously using I125- and I125-labeled antigen has been confirmed by direct staining with fluorescent antibodies. A fine web of phagocytic reticulum in primary follicles was found to be responsible for antigen localization in this area. The nature of this web was confirmed by studies of the localization of colloidal carbon. This unique feature of primary follicles is discussed in relation to its importance in the induction of immune responses, our belief being that the great surface area of antigen retaining cytoplasm in primary follicles is responsible for the appearance of germinal centers in these particular parts of the node.

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