Mullins et al. (Cancers, 2019) investigated the functionality of B cells in clinical tumor samples of patients with colorectal cancer.
The authors of the paper proof that the tumor infiltrating B cells can actively secrete immunoglobulins by performing an IgA/IgG/IgM FluoroSpot. The secretion profile of cells directly isolated from the tumor were analyzed using FluoroSpot.
In detail, the researchers found more IgA- than IgG-secreting cells, and even less IgM-secreting cells. Additionally, they discovered a correlation between IgG secretion with the number of MHCII-expressing cells (= antigen-presenting cells, including B cells). They also noted that Ig secretion seems to be increased in primary tumors compared to metastases.
Altogether, these findings support the hypothesis that tumor infiltrating B cells have a dual function in antigen presentation and anti-tumor immunoglobulin production.
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