A highlight on CD4+ T-cells in the spleen in a rat model of rheumatoid arthritis and possible therapeutic effect of omega-3. Histological and Immunofluorescence study

•Rheumatoid arthritis (RA) induced noticeable structural changes in the spleen.•Progressive RA showed extensive expression of AntiCD4 Monoclonal Antibodies.•Plasma cells, dendritic cells and Anitschkow cells were identified in the spleen in RA.•Omega-3 significantly improved the structure of the spleen as detected by both histological and immunofluorescence studies. Rheumatoid arthritis (RA), a primary chronic articular disease with wide range of extra-articular and systemic effects. The spleen is one of the most affected organs in RA. CD4+ T cells play an important role in initiation, maintenance and control of the disease. This work was designed to study the histological changes occurring in the spleen in a rat model of RA and to assess the effect of treatment with omega-3 alone, with special refer to the role of CD4+ T-cells. Thirty male albino rats were divided into four groups; control group, early and progressive RA groups and omega-3 treated group. RA was induced in rats of groups II, III and IV by a single subcutaneous injection of complete Freund’s adjuvant (CFA). Samples were taken after two and four weeks of the CFA injection (in early and progressive RA groups respectively). Treatment with omega-3 (300 mg/kg/day in a single, daily oral dose) started two weeks after CFA injection in rats of group IV and continued for another two weeks. Spleen specimens were collected at the appropriate times and processed to obtain paraffin blocks. Sections were then stained for histological and immunofluorescence studies. Both, early and progressive RA induced noticeable structural changes in the spleen. Thickened capsule and trabeculae and marked congestion of the blood sinusoids of the red pulp were evident. Expansion of the white pulp and areas of mononuclear cellular infiltration were seen, especially in progressive RA. Affection of blood vessel walls was also noticed. Immunofluorescence study showed extensive expression of Anti-CD4 Monoclonal Antibodies especially in progressive RA. Treatment with omega-3 significantly improved the structure of the spleen as detected by both histological and immunofluorescence studies. Omega-3 treatment ameliorated the structural damage of the spleen caused by experimental induction of RA.