CTLA4

CTLA4 (cytotoxic T-lymphocyte-associated protein 4) is a gene that makes the CTLA4 protein, which is a member of the family of immunoglobulin genes. The protein inhibits the activity of T cells, a type of white blood cell. 

Variations in this gene have been associated with: insulin-dependent diabetes mellitus (type 1 diabetes), Graves disease, Hashimoto thyroiditis, celiac disease, thyroid issues, systemic lupus erythematosus, thyroid-associated orbitopathy, rheumatoid arthritis, Addison's disease, and some cancers including melanoma. 

CTLA-4 is a protein receptor that functions as an immune checkpoint and downregulates immune responses. CTLA4 is constitutively expressed in regulatory T cells but only upregulated in conventional T cells after activation – a phenomenon that is particularly notable in cancers. It acts as an "off" switch when bound to CD80 or CD86 on the surface of antigen-presenting cells.

In general, it's much better to have more CTLA activity, except in cases of cancer in which you want a more powerful immune response.  Curcumin and flavonoids have an agonist effect on this protein.