Which of the following is a major cell infiltrate in rheumatoid arthritis?
Ref. Robbins Pathology. 9th edition. Page. 1209
Rheumatoid Arthritis
CD4+ T helper (TH) cells may initiate the autoimmune response in RA by reacting with an arthritogenic agent, perhaps microbial or a self-antigen 

IFN-γ from TH1 cells activates macrophages and resident synovial cells.
IL-17 from TH17 cells recruits neutrophils and monocytes.
TNF and IL-1 from macrophages stimulates resident synovial cells to secrete proteases that destroy hyaline cartilage.
RANKL expressed on activated T cells stimulates bone resorption.

Microscopy:
The characteristic histologic features include

Synovial cell hyperplasia and proliferation
Dense inflammatory infiltrates (frequently forming lymphoid follicles) of cd4+ helper t cells, b cells, plasma cells, dendritic cells, and macrophages
Increased vascularity due to angiogenesis
Fibrinopurulent exudate on the synovial and joint surfaces;
Osteoclastic activity in under- lying bone
CD4+helper cell
Macrophage
Lymphocyte
Dendritics cells