During the primary splenic response to the T‐independent type 2 (TI‐2) antigen (4‐hydroxy‐3‐nitrophenyl) acetyl (NP)‐Ficoll, small numbers of antigen‐specific B cells have entered S phase of the cell cycle 24 h after intraperitoneal immunization. These are distributed in all splenic compartments  (T zones, marginal zones, follicles, and red pulp), indicating early proliferation induced by NP‐Ficoll does not require accessory signals delivered in a particular splenic microenvironment. Subsequently B blasts accumulate selectively in the outer T zone areas, but exponential growth leading to plasma cell production occurs only in extra‐follicular foci. This growth peaks after 5 days, but 20 % of peak numbers of antibody‐containing cells are still present 3 months after immunization and 9 % of these cells are proliferating. It is unclear if these late plasmablasts are sustained by self‐renewal or continued recruitment of virgin cells into the response. Unlike TD and TI‐1 responses NP‐specific memory cells do not accumulate in the splenic marginal zones. The level of Cγ3 switch transcripts increases during the first 24 h of the response, but does not increase further during exponential plasmablast growth.