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Abstract
Chickens given an intravenous injection of human serum albumin (HSA) produced a rapid rise of antibody to a peak at 8–9 days, followed by a rapid decline. Plasma cells containing anti-HSA appeared in the spleen at 24 hr after injection. Evidence is presented that early produced antibody causes the localisation of antigen (HSA), presumably as complexes, to cells in the white pulp of the spleen at the periphery of ellipsoids (Schweigger-Seidel sheaths) by 24–32 hr. Inspection of a series of tissue sections shows that antigen-bearing cells appear to migrate through the white pulp and subsequently to appear (88 hr–6 days) as dendritic cells within germinal centres, which originated in the angle between the diverging penicillary arterioles at their point of origin from the central arteriole of the white pulp. A hypothesis is advanced that accounts for the formation of germinal centres by a process of progressive capture and aggregation of lymphocytes at the surface of antigen-bearing dendritic cells. This process is discussed in relation to the progressive increase of avidity in antibody synthesised later in the immunological response or after a secondary stimulus.
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