Helpful in understanding the mutation of Bruton's tyrosine kinase gene (Btk) which plays an crucial role in B-cell development To study the expression of VH gene in spleen Reveal the crucial role of IgM in preventing the infection of Crytococccus neoformans from lungs to the brain in chronic pulmonary infection model Role of BCR in TACI expression (T cell-independent type 1 Ag such as LPS which stimulate BCR). This evidence concerns the gene CD40LG and infection.