L. helveticus oral administration ↓ joint swelling; ↓ body weight loss; ↓ serum CII-specific IgG and IgG1; L. helveticus intraperitoneal inoculation ↓ arthritis incidence; ↓ joint damage; ↓ serum IL-6; ↓ total B-cells; ↓ CD4+ T cells in the inguinal LNs. Here, CD4 is linked to arthritic joint disease.