Homeostatic and functional analysis of mature B cells in λ5-deficient mice

The peripheral B-cell pool is in dynamic equilibrium and is controlled by a variety of factors. The rate of generation of B cells can influence both the composition and size of the peripheral B-cell compartment. Mice deficient for λ5 gene expression have a block in early B-cell development leading to a markedly reduced number of peripheral B cells. To address the question of how this early developmental block influences the composition of the B-cell pool, we have analyzed mature B-cell subpopulations in λ5-deficient mice. In analogy with other situations of B lymphopenia, the proportion was increased but not the absolute number of marginal-zone B cells, whereas those of follicular B cells were decreased. Immunohistology revealed that B-cell follicles were smaller in overall size and contained a prominent B-cell replete marginal zone. BrdU labelling kinetics showed slower turnover of follicular as well as of marginal-zone B cells. Functionally, λ5^-/- mice were able to mount not only primary but also secondary thymus-dependent as well as thymus-independent responses, albeit mostly at reduced levels.