Methods to polarize monocytes into macrophages are quite diverse, I think maybe we need our own optimization for our lab, and THP-1 is plastic enough to be treated with various stimulants to be maturated into our expected macrophage phenotype. Cytokines can be used generally around 5-10 ng/mL. Immune complexes plus LPS treatment is typically used for polarizing monocytes into M2b subset, while LPS alone is for M1. I have experience with LPS treatment for M1 and it's 100 ng/mL. My suggestion is to use IgG coated plates available in the market and treat THP-1 with 100 ng/mL LPS to polarize into M2b phenotype.

Did you try Vitamin D3?

@ Adhyatmika thanks for your suggestion. I did as you suggest and I will tell you the results of the exps. @ Hernández I didn't know that Vit D3 could polarize Macrophages in M2b. I'll take it in mind thanks.