B-cell maturation starts with B-cell precursors in the bone marrow. These precursors progress to becoming hematogones (various stages of immature B-cells in the bone marrow) and then become early maturing B-cells in the bone marrow. These early maturing B-cells then leave the bone marrow and end up in secondary lymphoid tissues (e.g. Lymph nodes, Mucosa Associated Lymphoid Tissue or Spleen) where they finish their maturation process upon antigen stimulation (During pre-antigen stimulation, these B-cells are predominantly in primary follicles and upon antigen stimulation they enter the germinal center of secondary follicles where somatic hypermutation and class switching occurs that eventually give rise to memory B-cells and plasma cells).
As opposed to B-cells that have surface bound immunoglobulins (Ig), the Ig of plasma cells are cytoplasmic because they are made to be secreted. Additionally, as opposed to both B-cells and T-cells which circulate in the peripheral blood, plasma cells are usually absent in blood.
Note: All B-cells express some level of CD19 and as antigen presenting cells they would be expected to also express MHC class II molecules which explains the expression of HLADR (a MHC class II) on all B-cells (from early B-cells to plasma cells). |
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