**4.1.3 B Cells**

Immunoglobulin deposition by B cells in BCA stroma can be detrimental to disease progression and the accumulation of autoantibodies produced by B cells and deposited in the stroma correlates with poor prognosis (Fernandez Madrid *et al*., 2005). An increase in serum IgG correlates with an increase in TAM numbers which, in turn, promotes angiogenesis in mouse mammary carcinoma, a process associated with poor clinical outcome. A proposed mechanism for the involvement of TAMs in B cell processes is the phagocytosis of IgG by macrophages. IgG engages Fcγ receptors, which stimulates VEGF secretion, increases angiogenesis and promotes tumour growth rate (Barbera-Guillem *et al*., 2002). The majority of stromal B cells localize to perivascular regions within tumours and chronic B cell activation promotes tumours by recruiting macrophages and activating an innate immune response. However, the role of B cells in BCA progression is complicated since, for example, B cells may also recruit antigen presenting cells, such as CD8+ T cells and dendritic cells which help to eradicate neoplasms.
