Cystic fibrosis and HLA

HLA frequencies and associations in cystic fibrosis

Cystic fibrosis (CF) is classically attributed to the dysfunction of the single CF transmembrane conductance regulator gene. The incidence of human leukocyte antigen (HLA) polymorphisms in different CF-associated diseases raises the question of an unequal distribution of HLA genotypes in CF. This study aimed to evaluate HLA gene frequencies and possible associations in CF patients compared with a control population. Frequencies of HLA-DRB1, HLA-DQA1 and HLA-DQB1, performed by intermediate resolution typing using Luminex sequence-specific oligonucleotide, and epitope counts were similar in 340 CF patients when compared with 400 control subjects. In conclusion, HLA-DRB1, -DQA1 and -DQB1 do not seem to influence susceptibility to CF. Whether HLA plays a role in the severity of CF disease needs to be investigated.

HLA class II polymorphism in cystic fibrosis. A possible modifier of pulmonary phenotype

Evolution of lung damage is highly variable in cystic fibrosis (CF) even in patients with the same cystic fibrosis transmembrane conductance regulator (CFTR) mutations. The analysis of genetic factors other than CFTR may help our understanding of genotype-phenotype relationships in CF. As human leukocyte antigen (HLA) class II polymorphism has been associated with a number of diseases including autoimmune and inflammatory diseases, asthma, and allergy, we investigated the possibility that HLA polymorphism contributes to CF-associated pulmonary inflammation. Among the 98 adult CF patients tested, the genotypic frequencies of DR4 and DR7 alleles (serologic group DR53) and DR7/ DQA*0201 haplotype were higher than in 39 selected control subjects without atopy (p </= 10(-)6, relative risk [RR] = 22, and p </= 5.10(-)4, RR = 27, respectively) and in a random population. No significant difference of these allelic distributions was found according to the CFTR genotype. In the CF patients, the DR7 allele was significantly associated with an increase in total IgE and with chronic Pseudomonas aeruginosa colonization (100% of DR7 versus 83% of non-DR7 patients being colonized, p < 0.05). Our results suggest that genetic factors known to modulate the immune response might contribute to chronic infection with Pseudomonas, increased total IgE, and pulmonary outcome in CF.

The major histocompatibility complex influences the development of chronic liver disease in male children and young adults with cystic fibrosis

BACKGROUND/AIMS

Chronic liver disease is a well-recognised complication of cystic fibrosis. Recent reports suggest that its development is not determined by specific mutations within the cystic fibrosis gene; however, familial clustering of portal hypertension cases and inappropriate immune responses against liver membrane antigens demonstrated in children with cystic fibrosis and chronic liver disease suggest that other genetic loci may be relevant. As the major histocompatibility complex has an important immunoregulatory role, we have investigated for associations with this complex and chronic liver disease in cystic fibrosis.

METHODS

We have determined human leucocyte antigen class I (A and B) and class II (DR) phenotypes by serological tissue typing and class II (DR and DQ) and class III (complement component C4 and 21-hydroxylase) gene polymorphisms in 274 children and young adults with cystic fibrosis, of whom 82 had evidence of chronic liver disease with portal hypertension in 49, and 146 healthy controls.

RESULTS

A marked difference in human leucocyte antigen frequency was limited to DQ6, which was found in 66.7% of cystic fibrosis patients with liver disease compared to 32.9% of patients with no liver disease (Pc < 0.03) and 28.8% of controls (Pc < 0.006). An increased frequency of the two antigens in strong linkage disequilibrium with DQ6 was also observed within this patient group, namely DR15 and B7. When the patients were stratified for the presence of portal hypertension, these observations were confirmed, but the human leucocyte antigen associations were significant only for male patients and there was no association with the age of onset of liver disease.

CONCLUSIONS

These data suggest that the haplotype B7-DR15-DQ6 may carry an increased risk of development of liver disease in male cystic fibrosis patients.

Cystic fibrosis-related diabetes is associated with HLA DQB1 alleles encoding Asp-57- molecules

The incidence of insulin-dependent diabetes in individuals with cystic fibrosis is nearly 100 times greater than in the general population. In the latter group, strong associations with specific HLA DQA1 and DQB1 alleles have been observed. To determine if a similar distribution of alleles occurs in cystic fibrosis patients with diabetes, a cohort of these individuals was typed for DQA1 and DQB1 alleles. HLA DQB1*0201 (Asp57-) was more frequent in diabetics compared to controls (40.4 vs 28%), while the frequency of alleles encoding Asp57+ molecules was lower in diabetics relative to both the cystic fibrosis-only controls (P = 0.025) and the general population (P = 0.008). The presence of at least one protective DQA1-DQB1 heterodimer (i.e., Arg52- and Asp57+, respectively) in cis or trans was significantly lower in the diabetics than in either of the control groups. Thus, the HLA alleles known to be associated with insulin-dependent diabetes mellitus in the general population are also found in diabetics with cystic fibrosis.

Absence of an association between HLA typing in cystic fibrosis arthritis and hypertrophic osteoarthropathy

Fourteen patients with cystic fibrosis arthritis and eight patients with cystic fibrosis and hypertrophic osteoarthropathy were typed for HLA-A, B, C, DR, and DQ antigens and were compared with age and sex matched controls with cystic fibrosis. The diagnosis of cystic fibrosis arthritis and hypertrophic osteoarthropathy was confirmed by radiography and bone scanning. The prevalence of HLA-A, B, C, D, antigens in the cystic fibrosis group (44 patients) did not differ from that in the control group. A comparison between patients with cystic fibrosis arthritis or hypertrophic osteoarthropathy and their respective controls did not show any significant differences in HLA prevalence. It is concluded that HLA antigens may not be a factor in the susceptibility of patients with cystic fibrosis to cystic fibrosis arthritis or hypertrophic osteoarthropathy.

Correlation of phenotypic and genetic heterogeneity in cystic fibrosis: variability in sweat electrolyte levels contributes to heterogeneity and is increased with the XV-2c/KM19 B haplotype

We have reinvestigated a classification of clinical heterogeneity among cystic fibrosis (CF) patients that we previously reported and investigated the possible relationship of the identified CF subgroups to haplotypes around the CF gene and to HLA-DR haplotypes. Age-corrected values for sweat electrolytes, rate of progression of lung disease as assessed by Brasfield chest x-ray scores, and severity of pancreatic insufficiency as assessed by daily supplemented enzyme dosage were obtained for 55, 59, and 59 patients, respectively. XV-2c and KM19 RFLPs were determined by hybridization to TaqI and PstI digests of human genomic DNA, respectively, and analysis of mutations by PCR amplification followed by allele-specific oligo-deoxynucleotide hybridization was performed for 29 patients. HLA-DR restriction fragment length polymorphisms (RFLPs) were determined by hybridization of cDNA beta 1 and genomic DQ alpha probes to TaqI digests of human genomic DNA. The results show that the previous subdivision on the basis of age-corrected levels of sweat electrolytes, as well as measures of severity of lung disease and pancreatic disease, is valid. In addition, the C and D haplotypes are associated with lower age-corrected sweat sodium level. No significant relationship between CF haplotypes and the other two disease variables or between HLA-DR haplotypes and any of the clinical variables was found.

The musculoskeletal manifestations of cystic fibrosis

Twenty-seven patients with CF and joint complaints were reviewed. Twelve patients had arthritis, 11 had HPO, and four had symptoms of mechanical neck and back pain. We have confirmed the association of CF with an episodic form of arthritis. For the first time, we have reported that a subgroup of these patients later develop persistent synovitis with progressive asymmetric, erosive disease. The etiology of CF arthritis is unclear, but may relate to chronic infection and immune complex mechanisms. CF arthritis can be contrasted with CF induced HPO, which is associated with worse lung disease, a male predominance, and an older mean age of onset of symptoms. Mechanical neck and back pain may relate to an associated scoliosis or kyphosis in CF.