Culture them with anti-BCR antibodies for 3 days. you will see large amounts of IL-4, IL-10, etc.

Could only find one paper where they have done this.

Article Efficient Culture of Human Naive and Memory B Cells for Use as APCs

Co-culture of T and B cells

"PBMC were thawed and labeled with carboxyfluorescein succinimidyl ester (CFSE, Invitrogen). T cells were isolated by negative selection with the EasySep Human T Cell Enrichment Kit (STEMCELL Technologies) from CFSE-labeled PBMC. The purities of CD3+ T cells (as determined by flow cytometry) were greater than 98% after enrichment. Frozen CD B cells were thawed and counted. Both T and CD B cells were suspended well before co-culture.

Equal numbers (1 × 104 each) of T and CD B cells per well were co-cultured in 96-well U-bottom plates (Fisher Scientific) in 100 µl per well of R5 medium without exogenous cytokines. For alloreactive T-cell proliferation studies, the plates were incubated at 37°C in a 5% CO2- humidified incubator for 5 days. For microbial antigen-specific T-cell proliferation studies, the plates were incubated for 7 days. Tetanus toxoid from Clostridium tetani (List Biological Laboratories), recombinant influenza HA (H3 A/Wisconsin/67/2005, kindly provided by S.C. Harrison), and recombinant B. anthracis PA (BEI Resources) were used in antigen-specific T-cell proliferation studies. T cells were treated with equal numbers of anti-CD3/CD28 Dynabeads® (Invitrogen) as positive controls in both alloreactive and microbial antigen-specific T-cell proliferation studies."

I guess you could just skip CFSE staining and collect the supernatants after 3-5 days for cytokine analyses.