The distribution of immunoglobulin and other plasma proteins in human reactive lymph nodes

The distribution of immunoglobulin, transferrin and albumin in human reactive lymph nodes was determined by the unlabelled antibody peroxidase‐antiperoxidase (PAP) method and correlated with the structure of the nodes. All the nodes contained secondary lymphoid follicles which showed polarity towards a lymph sinus, usually the marginal sinus. The lymphatic sinuses were usually dilated. Various types of reticulum cells were demonstrated effectively by the metalophil method. Intracellular and extracellular antigen was well shown in paraffin sections of tissues fixed in buffered formaldehyde containing 5 per cent. acetic acid but cryostat sections were superior for surface Ig. The lymphocyte corona of each follicle reacted for surface immunoglobulin (μ, α, δ κ and λ chains). A polyclonal population of immunoglobulin‐containing cells (centrocytes, centroblasts and plasma cells) was present in the follicle centre and numerous plasma cells were often found in the interfollicular areas; each of these cells contained one heavy and one light chain. The many other sites that reacted for immunoglobulin contained not only several heavy chains and both light chains but also transferrin and albumin: these sites included lymphocyte‐like cells in the interfollicular areas; histiocytic, dendritic and fibroblastic reticulum cells; clusters of lymphocytes associated with dendritic reticulum cells; clusters of lymphocytes associated with dendritic reticulum cells; the cells lining the lymphatic sinuses and the intrasinusoidal reticulum cells; endothelial cells of the high endothelial venules; “extracellular” material in the germinal centres. The lymphatic endothelium and intrasinusoidal reticulum cells differed from the other sites, however, in reacting strongly for α and J chain and very weakly for γ chain. The fact that in reactive lymphoid tissue many cells contain several plasma proteins makes it difficult to draw conclusions about the role that such cells may have in the immune system. The morphological structure and immunohistochemical findings in ractive nodes are contrasted with the findings in lymphomas.