The paper reviews the current literature on the dysregulation of the immune response system in major depressive disorder (MDD) and bipolar disorder (BD), focusing on studies using inflammatory markers to discriminate between the two disorders. The authors highlight the importance of understanding distinct immune profiles for differential diagnosis and personalized treatment strategies. Key findings include: 1. **C-reactive Protein (CRP)**: Higher CRP levels are observed in both MDD and BD, but BD patients show more significant increases during manic episodes. CRP levels are not stable and fluctuate with illness phases. 2. **Blood Count Ratios**: Neutrophil/Lymphocyte ratio (NLR) and Platelet/Lymphocyte ratio (PLR) are higher in BD compared to MDD, suggesting greater endothelial dysfunction in BD. 3. **Cytokines and Chemokines**: - **Pro-inflammatory Cytokines**: IL-6 and TNF-α are consistently elevated in both MDD and BD. - **Anti-inflammatory/Cytokines**: IL-10 is higher in MDD, while IL-4 levels are increased in manic phases of BD. - **Chemokines**: CCL2 and IL-8 are more prominent in BD, indicating greater cell trafficking. 4. **Monocyte Gene Expression**: Monocytes in BD show overexpression of inflammatory genes, while MDD monocytes exhibit abnormal expression of genes involved in apoptosis, growth, lipid metabolism, and redox reactions. 5. **T Cell Populations**: - **Th1/Th2**: MDD patients show an increase in Th1/Th2 ratio, while BD patients have a shift towards Th2. - **Th17 Cells**: Higher levels of Th17 cells are associated with BD, but their role is complex and context-dependent. - **T Regulatory Cells**: BD patients show higher levels of Tregs compared to healthy controls, but findings are mixed. The paper concludes that while MDD and BD share some immune biomarkers, distinct profiles exist, particularly in the involvement of the inflammatory response system. These differences may explain the varying clinical presentations and treatment responses in these disorders. Further research is needed to clarify the role of immune-related biomarkers in differentiating and treating mood disorders.The paper reviews the current literature on the dysregulation of the immune response system in major depressive disorder (MDD) and bipolar disorder (BD), focusing on studies using inflammatory markers to discriminate between the two disorders. The authors highlight the importance of understanding distinct immune profiles for differential diagnosis and personalized treatment strategies. Key findings include: 1. **C-reactive Protein (CRP)**: Higher CRP levels are observed in both MDD and BD, but BD patients show more significant increases during manic episodes. CRP levels are not stable and fluctuate with illness phases. 2. **Blood Count Ratios**: Neutrophil/Lymphocyte ratio (NLR) and Platelet/Lymphocyte ratio (PLR) are higher in BD compared to MDD, suggesting greater endothelial dysfunction in BD. 3. **Cytokines and Chemokines**: - **Pro-inflammatory Cytokines**: IL-6 and TNF-α are consistently elevated in both MDD and BD. - **Anti-inflammatory/Cytokines**: IL-10 is higher in MDD, while IL-4 levels are increased in manic phases of BD. - **Chemokines**: CCL2 and IL-8 are more prominent in BD, indicating greater cell trafficking. 4. **Monocyte Gene Expression**: Monocytes in BD show overexpression of inflammatory genes, while MDD monocytes exhibit abnormal expression of genes involved in apoptosis, growth, lipid metabolism, and redox reactions. 5. **T Cell Populations**: - **Th1/Th2**: MDD patients show an increase in Th1/Th2 ratio, while BD patients have a shift towards Th2. - **Th17 Cells**: Higher levels of Th17 cells are associated with BD, but their role is complex and context-dependent. - **T Regulatory Cells**: BD patients show higher levels of Tregs compared to healthy controls, but findings are mixed. The paper concludes that while MDD and BD share some immune biomarkers, distinct profiles exist, particularly in the involvement of the inflammatory response system. These differences may explain the varying clinical presentations and treatment responses in these disorders. Further research is needed to clarify the role of immune-related biomarkers in differentiating and treating mood disorders.