Flow cytometric assessment of the different patterns of immune response in osteoarthritis vs rheumatoid arthritis

الملخص EN

Aim of work : it has been suggested that osteoarthritis (OA) is induced by mechanical stress manifested by cartilage destruction with no or minimal involvement of the immune response as compared to that in rheumatoid arthritis (RA).

This study is a trial to investigate the hypothesis that the immune response has a critical role in the pathogenesis of OA.

Methodology : this work was performed on 2 groups of patients: The 1st group comprised 20 primary OA knee patients and the 2nd group consisted of 18 RA patients as autoimmune controls.

Patients of both groups were diagnosed according to the revised criteria of the American College of Rheumatology (ACR).

All patients were subjected to : complete history taking, clinical examination, degree of severity of OA, disease activity for RA patients and routine laboratory assays.

Radiological examinations were done for the wrists, hands and both knees for both RA and OA patients.

The different patterns of immune response : CD3+ CD19- (T-cells), CD8- CD4+ (T-helper), CD4- CD8+ (T-cytotoxic), the ratio of CD4 / CD8 T-cells, CD3- CD19+ (B cells) and CD3-CD16+ 56+ (Natural Killer cells) (NK) cells from peripheral blood (PB) of both groups, were estimated quantitatively with multicolor flow cytometer.

Results : The RA patients group included 3 males (16.7 %) and 15 females (83.3 %), while the OA group were 2 males (10 %) and 18 females (90 %).

The age of RA patients ranged between 21-55 years with a mean + SD of 46.17 + 5.02.

For the OA group it was between 35-59 years with a mean + SD of 43.10 + 7.62.

As regards the disease duration, it ranged between 2-15 years (3.67 + 2.25) and between 2-22 years (4.35 + 2.68) for RA and OA patients respectively.

Assessment of disease severity for knee OA revealed that 14 patients (70 %) were severely affected, 4 patients (20 %) were moderate and 2 patients (10 %) were mild.

The mean + SD for score of disease activity (DAS) for RA patients was 7 + 1.01.

Statistical analysis: There was no statistical significant difference between both groups of RA and OA regarding; age, disease duration, the immune profile; the estimated percentages of lymphocytes, CD4+T-cells, CD8+T-cells, B cells, NK cells, the ratio of CD4 / CD8 and complement3 (C3) (p > 0.05).

The statistical significant differences were present between both groups in relation to; the platelets (Plat), the total leucocyte count (TLC), erythrocyte sedimentation rate (ESR), hemoglobin (Hb %), C-reactive protein (CRP) and rheumatoid factor (RF).

Regarding the statistical correlation between the estimated CD4+T-cells %, CD8+T-cells % and other evaluated clinical and laboratory data, we fond that : (1) In OA: group lymphocytes%, C3 and ratio of CD4/ CD8 had positive statistical significant correlations to estimated CD4+T-cells %.

On the other hand, lymphocytes % and ratio of CD4 / CD8 had positive and negative statistical significant correlations respectively to estimated CD8+ T-cells %.

(2) In RA group: the lymphocytes % and ratio of CD4/CD8 were the only parameters that had positive statistical significant correlation to estimated CD4+T-cells %.

There were negative statistical significant correlations between estimated CD4+ T-cells % and CRP, C3, RF and DAS ; while, the ratio of CD4 / CD8 was the only parameter that had a negative statistical significant correlation to estimated CD8+ T-cells %.

Conclusion : the previous results reflect the similarity of immune profile in both RA and OA patients.

This raised the possibility that abnormalities in T-cells and its subpopulations may contribute to the pathogenesis of OA.

We propose that patients having such cell populations response similar to RA patients predisposing them to chronic, progressive immune response in the synovial membrane (SM) with cartilage destruction.

Targeting of the cascade that leads to this immune response may open new avenues for treating OA.