Macrophage migration inhibitory factor (MIF), an immunoregulatory cytokine that has pro‐inflammatory, hormonal and enzymatic activities, has been found to be markedly increased in the serum of patients with inflammatory bowel disease (IBD).1,2 MIF‐deficient mice failed to develop disease1 and blockage with anti‐MIF antibody reduced disease activity.1,2 Finally, functional polymorphisms of the human MIF gene have been associated with increased susceptibility to inflammatory and autoimmune diseases.3 These findings prompted us to investigate the potential association of the functional MIF −173G/C and −794 (CATT)n gene variants with the susceptibility and clinical expression of IBD.
We studied a case–control cohort (cohort 1) comprising 336 patients with Crohn's disease and 287 patients with ulcerative colitis from south Spain and 361 controls from the same area. An additional cohort (cohort 2) was analysed, comprising 325 patients with Crohn's disease, 347 patients with ulcerative colitis and 526 controls from Madrid. Table 1 shows the clinical characteristics of both cohorts separately. MIF −173 and MIF CATT repeat genotyping was carried out as described previously.4
Table 1 Clinical features of 558 Spanish patients with Crohn's disease and 472 Spanish patients with ulcerative colitis.
| Cohort 1 | Cohort 2 | |
|---|---|---|
| Ulcerative colitis | ||
| Sex (% M) | 49 | 43 |
| Mean (SD) age at onset (y) | 32.3 (13.7) | 37.5 (12.3) |
| Mean (SD) disease duration (y) | 8.1 (6.4) | 11.8 (7.6) |
| Smoking habits (%) | ||
| Never | 51.9 | 43.2 |
| Ex/current | 48.1 | 56.8 |
| Extraintestinal manifestations | 41.7 | 46.6 |
| Cutaneous (%) | 13.7 | 15.8 |
| Articular (%) | 35.8 | 36.8 |
| Ocular (%) | 3.6 | 3.2 |
| Disease location (%) | ||
| Left sided | 54.8 | 58.6 |
| Extensive colitis/pancolitis | 45.2 | 41.4 |
| Surgery (%) | 15.9 | 12.1 |
| Immunosuppression (%) | 26 | 23 |
| Crohn's disease | ||
| Sex (% M) | 48 | 47.1 |
| Mean (SD) age at onset (y) | 29.2 (11.7) | 27.3 (13.4) |
| <40 (A1) | 82.3 | 80.1 |
| >40 (A2) | 17.7 | 19.9 |
| Mean (SD) disease duration (y) | 7.9 (6.1) | 11 (6.6) |
| Smoking habits (%) | ||
| Never | 49.2 | 53.9 |
| Ex/current | 50.8 | 46.1 |
| Disease location | ||
| Ileal (L1) | 41.2 | 47.9 |
| Colonic (L2) | 16.4 | 16.4 |
| Ileocolonic (L3) | 38.7 | 32.2 |
| Upper GI tract (L4) | 3.7 | 3.4 |
| Disease behaviour | ||
| Inflammatory (B1) | 36.7 | 43.2 |
| Structuring (B2) | 25.3 | 15.1 |
| Perforating (B3) | 38 | 41.8 |
| Extraintestinal manifestations | 37.8 | 36.9 |
| Surgery (%) | 43.2 | 41.5 |
| Immunosuppression (%) | 46.8 | 45.1 |
| Infliximab (%) | 12.3 | 10.8 |
GI, gastrointestinal; M, male.
Evidence for association of MIF and IBD was found when the MIF −173G/C genotypes and alleles were compared between patients with IBD and controls from cohort 1 (table 2). The MIF −173*C allele was associated with an increased susceptibility to IBD (p = 0.002). Similarly, an increased −173*C allele frequency was observed in patients with IBD in cohort 2 (p = 0.034). In the combined analysis, the odds ratio (OR) for the estimated risk for the MIF −173*C allele was 1.37 (95% confidence interval 1.1 to 1.6), with an overall p = 0.001.
Table 2 Genotype and allele frequencies of MIF −173G/C in patients with inflammatory bowel disease and in controls.
| MIF −173G/C | Genotypes, (n %) | Alleles, (n %) | OR (95% CI) | ||||
|---|---|---|---|---|---|---|---|
| GG | GC | CC | G | C | p Value* | ||
| Cohort 1 | |||||||
| Controls (n = 361) | 275 (76.2) | 81 (22.4) | 5 (1.4) | 631 (87.4) | 91 (12.6) | ||
| IBD (n = 623) | 423 (67.9) | 178 (28.6) | 22 (3.5) | 1024 (82.2) | 222 (17.8) | 0.002 | 1.5 (1.1 to 1.9) |
| CD (n = 336) | 227 (67.5) | 94 (27.9) | 15 (4.5) | 548 (81.5) | 124 (18.4) | 0.002 | 1.5 (1.1 to 2.0) |
| UC (n = 287) | 196 (68.3) | 84 (29.3) | 7 (2.4) | 476 (82) | 98 (17) | 0.02 | 1.4 (1.04 to 1.9) |
| Cohort 2 | |||||||
| Controls (n = 526) | 406 (77.2) | 107 (20.3) | 13 (2.5) | 919 (87.3) | 133 (12.6) | ||
| IBD (n = 672) | 484 (73.2) | 165 (23.5) | 23 (3.3) | 1133 (84.3) | 211 (15.7) | 0.034 | 1.2 (1.01 to 1.6) |
| CD (n = 325) | 239 (73.5) | 78 (24) | 8 (2.5) | 556 (85.5) | 94 (14.4) | 0.2 | 1.1 (0.8 to 1.5) |
| UC (n = 347) | 245 (72.9) | 87 (23) | 15 (3.9) | 577 (83.1) | 117 (16.8) | 0.01 | 1.4 (1.07 to 1.8) |
| Combined | |||||||
| Controls (n = 887) | 681 (76.7) | 188 (21.3) | 18 (2) | 1550 (87.4) | 224 (12.6) | ||
| IBD (n = 1295) | 907 (70) | 343 (26.4) | 45 (3.4) | 2157 (83.3) | 433 (16.7) | 0.001 | 1.3 (1.1 to 1.6) |
| CD (n = 661) | 466 (70.5) | 172 (26) | 23 (3.5) | 1104 (83.5) | 218 (16.5) | 0.002 | 1.3 (1.1 to 1.6) |
| UC (n = 634) | 441 (70.9) | 171 (25.7) | 22 (3.3) | 1053 (83) | 215 (17) | 0.001 | 1.4 (1.1 to 1.7) |
CD, Crohn's disease; IBD, inflammatory bowel disease; UC, ulcerative colitis.
*p Value of MIF −173* C allele.
Mantel–Haenszel test:
IBD pooled OR 1.37, 95% CI 1.1 to 1.6; p = 0.001.
CD pooled OR 1.34, 95% CI 1.1 to 1.6; p = 0.005.
UC pooled OR 1.4, 95% CI 1.1 to 1.7; p = 0.001.
Next, we analysed the prevalence of the MIF −173G/C variation in patients with Crohn's disease and ulcerative colitis independently. The MIF −173*C allele frequency was significantly higher in patients with ulcerative colitis from cohorts 1 (p = 0.02) and 2 (p = 0.01) compared with their respective controls. Similarly, the allele frequency of the MIF polymorphism in patients with Crohn's disease from cohort 1 was significantly higher than in controls (p = 0.002). When the entire population with IBD was subdivided into ulcerative colitis and Crohn's disease cohorts, the MIF −173*C allele was found to be associated with both disease subgroups (Crohn's disease, pooled OR = 1.3, p = 0.004; ulcerative colitis, pooled OR = 1.4, p = 0.001). No significant differences were observed in the distribution of CATTn genotype and allele frequencies between IBD, Crohn's disease, ulcerative colitis and controls in the two cohorts, when analysed independently or combined (data not shown). For the genotype–phenotype analysis, patients from cohorts 1 and 2 were grouped and analysed together, and no significant differences were observed.
Along with the data reported here, the observations that the MIF −173*C risk allele is related to high MIF expression5 and that serum MIF levels were markedly increased in patients with IBD1,2 support the involvement of MIF in the pathogenesis of IBD. Interestingly, transgenic overexpression of MIF renders mice markedly more susceptible to experimental colitis.6 High levels of MIF in patients with IBD might immobilise macrophages and facilitate their localisation at the intestinal mucosa, leading to the production of several inflammatory cytokines. Upregulation of MIF in both Crohn's disease and ulcerative colitis indicates that MIF might contribute to a broad spectrum of inflammatory responses via innate and acquired immune systems in IBD that may involve different pathogenic mechanisms.7
The MIF allele frequencies found in the Spanish population are similar to those reported in other white populations.3 It is remarkable that, although an increase in the MIF −173*C allele was observed in patients with ulcerative colitis compared with controls, the MIF −173*C allele was not associated with susceptibility to ulcerative colitis in the Japanese population.8
Regarding the genotype–phenotype analysis, we observed that MIF allele frequencies in the different ulcerative colitis and Crohn's disease subgroups were not significantly different when compared with other subphenotypes. It must be cautioned that the numbers in the ulcerative colitis and Crohn's disease subphenotype samples were small and should be expanded before the extent of associations can be properly assessed.
Autoimmune diseases such as IBD are presumed to have common underlying mechanisms and thus, some degree of shared genetic predisposition.9MIF genetic variants have been found to be associated with autoimmune diseases.3,4,5 These observations, together with our findings that MIF gene polymorphisms are associated with IBD, provide support for the notion that susceptibility to multiple autoimmune diseases may have some common susceptibility alleles or pathways.
Footnotes
Funding: This work was supported by grants from the Spanish Plan Nacional de I+D SAF2003‐03460 and SAF2006‐0398.
Competing interests: None.
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