Table 2
Summary of neuroinflammatory and immunological abnormalities observed in pure psychiatric disorders
| Abnormalities | Major depression | Bipolar disorder | Schizophrenia | OCD |
|---|---|---|---|---|
| Genetics | ||||
| Concordance | 37% to 38% [24] | 40% to 70% [25] | 40% to 50% [26] | 80% to 87% [27] |
| GWAS genes | Tryptophan hydroxylase-1, BDNF, 5-HTTLPR, PBRM1 [24] | Tryptophan hydroxylase-2, Voltage-gated Ca2+ channel α1C, PBRM1, D22S278, ANK3 [25] | GABAAR B2 subunit, COMT, Neuregulin-1, DISC1 [26] HLA (B, C, DRA1, and DRB1; antigen presentation, autoimmunity) [28] | EAAT3 (SLC1A1) [27] |
| Immunologic genes | Proteasome β4 subunit (antigen processing) [21], T-box 21 (T cell differentiation) [21], IL-1 [29], TNF-α [29], G-765C (COX-2) [30], BDNF [24] | BDNF gene [31]; consistent with decreased serum BDNF levels | S100B [32,33]; consistent with increased brain and CSF S100B levels | TNF-α [34] |
| Astroglia | ||||
| Density | Decreased (highly reproducible) [35-41]; few exceptions [42,43] | Reduced or no change [37,44-46] | Reduced or no change [37-39,47-49][42,50,51] | Insufficient data |
| TDO, KYNA | … | KYNA is increased [52,53] | Both are increased [21,52] | … |
| Oligodendroglia | ||||
| Density | Decreased [54-58] | Decreased [54,56-65] | Decreased [54-58,66] | Insufficient data |
| Microglial activation | ||||
| Trait and State markers | Trait: no [53,67,68]; State (suicidal): yes [22,68] | Mixed data [53,68,69] | Trait: no [70]; State (suicidal): yes [22,68] | Insufficient data; yet, Hoxb8 (-/-) mice exhibit OCD-like behavior [71,72] |
| IDO, KMO | Both are increased [29] | … | Both are decreased [21],[73] | … |
| Quinolinic acid | Increased [53] | … | … | … |
| Lymphocytes | ||||
| T cells, T regs, B cells | T cells are decreased [15,74]; T regs are decreased [15,74] | T regs are increased [75] | T cells are decreased [76]; ‘CD4+: CD8+ ratio’ is decreased [76]; B cells are increased [21,76] | ‘CD4+: CD8+ ratio’ is decreased [77] (normalized after SRI treatment) |
| EAAT | ||||
| EAATs 1,2 (astroglial) | Both are decreased in the DLPFC and ACC [78] | EAAT1 is increased, EAAT2 is decreased in PFC [79] | Both are increased in PFC [79-81], and thalamus [82] | … |
| EAATs 3,4 (neuronal) | EAAT4 is decreased in striatum [83] | Both are decreased in striatum [79] | EAAT3 is decreased in striatum [83]; Both are increased in PFC [79-81] and thalamus [82] | EAAT3 is decreased in CSTC circuitry [77,84] |
| Glutamate, GABA | ||||
| Post-mortem brain tissue | Glutamate and D-serine are increased in the frontal cortex [85,86] | Glutamate and D-serine are increased in DLPFC and hippocampus [86]. Increased glutamine in ACC/Parietal-OCC [78] | Glutamine synthetase is increased [87] | … |
| CSF, serum | Glutamate is increased in both; serum levels normalized after 5-week antidepressant course [85,86]; GABA is decreased in both [85,86] | … | … | CSF glutamate is increased [88]; normalized after one dose of ketamine (NMDAR antagonist) |
|
1H MRS | Glutamate is increased [85,89] Decreased glutamine synthetase, glutamine, and GABA (ACC, PFC, DMPFC, VMPFC, amygdala, hippocampi; normalized with ECT and disease remission) [78] | GLX is increased in medial PFC (ACC, DLPFC, parietal-OCC, OCC, insula, hippocampus) [78,79]; independent of disease state. | Glutamate is decreased in medial PFC (including ACC); Increased glutamine synthetase, glutamine, and ‘glutamine:glutamate ratio’ in PFC [90] | GLX is increased in left caudate and OFC (normalized after successful SRI treatment); GLX is decreased in ACC [84] |
| Cytokines (serum) | | | | |
| Phenotype | Proinflammatory are increased [91] | Proinflammatory are increased [92]; IL-1β, IL-1R, and IL-6 correlate with post-mortem brain mRNA expression [69] | Mixed data: antiinflammatory and/or proinflammatory, are increased [52,94,93] | Mixed data: TNF-α is increased or decreased; IL-6 is increased or no change; IL-1β is decreased [95] |
| Trait and State markers | Trait markers: TNF-α, IL-6, and sIL-2R are increased [91] State markers (suicidal): TNF-α and IL-6 are increased, and IL-2 is decreased [96]. | Depressive state: IL-6 Euthymic state: IL-4 Manic state: IL-2, IL-4, IL-6 [92] | Trait makers: IFN-γ, TNF-α, IL-12, sIL-2R, IL-1RA, sIL-2R [93] State markers: IL-1β, IL-6, TGF-β [93] | Trait markers: mixed data LPS-induced: TNF-α and IL-6 are decreased [95] |
5-HTTLPR, serotonin-transporter-linked polymorphic region; ANK3, ankyrin-3; ACC, anterior cingulate cortex; BDNF, brain-derived neurotrophic factor, BPD, bipolar disorder; COMT, catechol-O-methyl transferase; COX-2, cyclooxygenase 2; CSF, cerebrospinal fluid, CSTC, cortico-striatal-thalamic-cortico; DLPFC, dorsolateral prefrontal cortex; DMPFC, dorsomedial prefrontal cortex; EAAT, excitatory amino acid transporter: (EAATs 1 and 2 are expressed by astroglia, EAAT3 is expressed intracellularly in the post-synaptic neurons, and EAAT4 is expressed by Purkinje cells and frontal neurons); GABA, gamma aminobutyric acid; GLX1H MRS: (detectable glutamate, glutamine, gamma aminobutyric acid composite); GWAS, genome-wide association study (single nucleotide polymorphisms identified across the entire genome of those with a given disorder (fourth row); includes immunologic genetic abnormalities (fifth row) whenever applicable); 1H MRS, proton magnetic resonance spectroscopy; HLA, human leukocyte antigen; IDO, indoleamine-2,3-oxygenase; IFN-γ, interferon gamma; IL, interleukin, IL-1RA; interleukin 1 receptor antagonist; KMO, kynurenine monooxygenase; KYNA, kynurenic acid; MDD, major depressive disorder; OCC, occipital cortex; OCD, obsessive-compulsive disorder; OFC, orbitofrontal cortex; PBRM1, protein polybromo-1; PFC, prefrontal cortex; SRI, serotonin reuptake inhibitor; T regs, CD4+CD25+FOXP3+ T regulatory cells; TDO, tryptophan-2,3-dioxygenase, TGF-β, transforming growth factor beta; TNF-α, tumor necrosis factor alpha; VMPFC, ventromedial prefrontal cortex.
