Transitional B cell
Transitional B cells are
secondary lymphoid organs
such as the spleen.
Characteristic of transitional cells
The term "transitional B cell" was first used in
heat-stable antigen (HSA, CD24) relative to their mature counterparts and express the phenotypic surface markers AA4.[6]
T1 and T2
There are two transitional stages for the B cells in mouse, T1 and T2, with the T1 stage occurring from its migration from the bone marrow to its entry into the spleen, and the T2 stage occurring within the spleen where they developed into mature B cells.
Overall there is general agreement on the markers used to separate the subpopulations, although some differences exist in the number of subgroups and in the functional characteristics of the T2 population. T1 B cells are distinguished from the other subsets by the following surface marker characteristics: they are
CD21−CD23−, whereas T2 B cells retain high levels of surface IgM but are also IgD+CD21+ and CD23+.[8] Differences in functional characteristics of the T2 subpopulation reported by different laboratories are unexplained, although they might be due to differences in isolation strategies. In any case, there is consensus that T2 B cells clearly differ functionally from T1 B cells.[9]