Redundancy and absurd names in immunology.

In this short review, examples of unnecessary multiple names of cell membrane molecules, for example, immune checkpoints and cytokines, are presented. Moreover, ridiculous or inaccurate names, such as 'Regulated on activation, normal T-cell expressed and secreted' and 'tissue factor', are discussed.

EULAR study group on 'MHC-I-opathy': identifying disease-overarching mechanisms across disciplines and borders.

The 'MHC-I (major histocompatibility complex class I)-opathy' concept describes a family of inflammatory conditions with overlapping clinical manifestations and a strong genetic link to the MHC-I antigen presentation pathway. Classical MHC-I-opathies such as spondyloarthritis, Behçet's disease, psoriasis and birdshot uveitis are widely recognised for their strong association with certain MHC-I alleles and gene variants of the antigen processing aminopeptidases ERAP1 and ERAP2 that implicates altered MHC-I peptide presentation to CD8+T cells in the pathogenesis. Progress in understanding the cause and treatment of these disorders is hampered by patient phenotypic heterogeneity and lack of systematic investigation of the MHC-I pathway.Here, we discuss new insights into the biology of MHC-I-opathies that strongly advocate for disease-overarching and integrated molecular and clinical investigation to decipher underlying disease mechanisms. Because this requires transformative multidisciplinary collaboration, we introduce the EULAR study group on MHC-I-opathies to unite clinical expertise in rheumatology, dermatology and ophthalmology, with fundamental and translational researchers from multiple disciplines such as immunology, genomics and proteomics, alongside patient partners. We prioritise standardisation of disease phenotypes and scientific nomenclature and propose interdisciplinary genetic and translational studies to exploit emerging therapeutic strategies to understand MHC-I-mediated disease mechanisms. These collaborative efforts are required to address outstanding questions in the etiopathogenesis of MHC-I-opathies towards improving patient treatment and prognostication.

Down-regulation of ERAP1 mRNA expression in non-small cell lung cancer.

BACKGROUND: ERAP1 is a major aminopeptidase that serves as an editor of the peptide repertoire by trimming N-terminal residues of antigenic peptides, creating a pool of peptides with the optimal length for MHC-I binding. As an important component of the antigen processing and presenting machinery - APM, ERAP1 is frequently down-regulated in many cancers. Since ERAP1 expression has not yet been thoroughly investigated in non-small cell lung cancer (NSCLC), we decided to analyze ERAP1 mRNA levels in tissues collected from NSCLC patients. METHODS: Using real-time qPCR, we evaluated ERAP1 mRNA expression in samples of tumor and adjacent non-tumor tissue (serving as control tissue) from 61 NSCLC patients. RESULTS: We observed a significantly lower level of ERAP1 mRNA expression in tumor tissue (MedTumor = 0.75) in comparison to non-tumor tissue (MedNon-tumor = 1.1), p = 0.008. One of the five tested polymorphisms, namely rs26653, turned out to be significantly associated with ERAP1 expression in non-tumor tissue (difference [d] = 0.59 CI95% (0.14;1.05), p = 0.0086), but not in tumor tissue. The levels of ERAP1 mRNA expression did not affect the overall survival of NSCLC patients, either in the case of the tumor (p = 0.788) or in non-tumor (p = 0.298) tissue. We did not detect any association between mRNA ERAP1 expression level in normal tissue and: (i) age at diagnosis (p = 0.8386), (ii) patient's sex (p = 0.3616), (iii) histological type of cancer (p = 0.7580) and (iv) clinical stage of NSCLC (p = 0.7549). Furthermore, in the case of tumor tissue none of the abovementioned clinical parameters were associated with ERAP1 expression (p = 0.76). CONCLUSION: Down-regulation of ERAP1 mRNA observed in NSCLC tissue may be related to tumor immune evasion strategy. The rs26653 polymorphism can be considered an expression quantitative trait locus (eQTL) associated with ERAP1 expression in normal lung tissue.

The effect of LILRB1 but not LILRA3 gene polymorphism in immunopathology of ankylosing spondylitis-A parallel to KIR genes.

LILR and KIR receptors recognize HLA-B27 and may influence immune response in ankylosing spondylitis (AS) development. Purpose of the study was to analyse LILRB1/LILRA3 polymorphisms in AS. We observed a possible protective effect of the T allele of LILRB1 rs1061680:T>C and no association with insertion/deletion polymorphisms of LILRA3 with AS.

HLA-C*06:02-independent, gender-related association of PSORS1C3 and PSORS1C1/CDSN single-nucleotide polymorphisms with risk and severity of psoriasis.

Psoriasis vulgaris (PsV) is a common, chronic skin disease with a complex genetic and environmental etiology. We investigated, in 461 psoriatic patients and 454 healthy controls, the associations with psoriasis of four single-nucleotide polymorphisms (SNPs) from the psoriasis susceptibility 1 (PSORS1) interval: rs1062470 (PSORS1C1/CDSN), rs887466 (PSORS1C3), rs2894207 and rs10484554 (LOC105375015). The minor alleles of three SNPs (rs1062470A, rs2894207C and rs10484554T) strongly increased the disease risk (OR = 2.17, p < 0.0001; OR = 2.33, p < 0.0001 and OR = 2.68, p < 0.0001, respectively), whereas the minor A allele of rs887466 exerted a protective effect (OR = 0.73, p = 0.001). The strength of association for SNPs was the highest in patients with very early onset psoriasis (≤ 20 years), while in late onset psoriasis (> 40 years) the association was the weakest. The haplotype rs1062470A/rs887466G/rs2894207C/rs10484554T highly significantly increased the disease risk (OR = 3.58, p = 8.0e-027), while the haplotypes rs1062470G/rs887466A/rs2894207T/rs10484554C and rs1062470G/rs887466G/rs2894207T/rs10484554C were strongly protective (OR = 0.65, p = 0.002 and OR = 0.55, p = 2.4e-009, respectively). Additionally, we showed a HLA-C*06:02-independent gender-related effect of the rs887466A allele which was protective against psoriasis in males (OR = 0.61, p = 9.2e-005), but not in females (p = 0.66). We also demonstrated a correlation of PASI score value with rs1062470 genotype, and again only in male patients (p = 0.006) and HLA-C*06:02-independent. Our results show, for the first time, the male-only associations of the PSORS1C3 gene with psoriasis risk and of the PSORS1C1/CDSN gene with severity of disease. However, the age dependent associations need to be validated in larger sample sizes as well as in other populations.

The impact of HLA-G, LILRB1 and LILRB2 gene polymorphisms on susceptibility to and severity of endometriosis.

Endometriosis is a disease in which endometriotic tissue occurs outside the uterus. Its pathogenesis is still unknown. The most widespread hypothesis claims that ectopic endometrium appears as a result of retrograde menstruation and its insufficient elimination by immunocytes. Some reports have shown expression of non-classical HLA-G molecules on ectopic endometrium. HLA-G is recognized by KIR2DL4, LILRB1 and LILRB2 receptors on natural killer (NK) and other cells. These receptors are polymorphic, which may affect their activity. In this study we investigated whether HLA-G, KIR2DL4, LILRB1 and LILRB2 polymorphisms may influence susceptibility to endometriosis and disease progression. We used polymerase chain reaction (PCR), PCR-restriction fragment length polymorphism (PCR-RFLP) and allelic discrimination methods with TaqMan SNP Genotyping Assays for typing of 276 patients with endometriosis and 314 healthy fertile women. The HLA-G rs1632947:GG genotype was associated with protection against the disease and its severe stages; HLA-G rs1233334:CT protected against progression; LILRB1 rs41308748:AA and LILRB2 rs383369:AG predisposed to the disease and its progression. No effect of KIR2DL4 polymorphism was observed. These results support the role of polymorphisms of HLA-G and its receptors LILRB1 and LILRB2 in susceptibility to endometriosis and its progression.

The influence of KIR gene presence/absence polymorphisms on the development of periodontal disease in smokers and non-smokers.

INTRODUCTION: Periodontal diseases are highly prevalent inflammatory, multifactorial diseases. Smoking is one of the most important environmental risk factors for the development and severity of periodontal disease. Killer cell immunoglobulin-like receptors (KIRs) are members of the immunoglobulin (Ig) superfamily and play an essential role in the regulation of NK cell activity, allowing natural killer (NK) cells to sense and respond to human leukocyte antigen (HLA) class I. The aim of this study was to evaluate the influence of KIR gene presence/absence polymorphisms on the development of periodontal disease in smokers and non-smokers. MATERIAL AND METHODS: This study enrolled 400 Caucasian subjects (age range 25-69 years) from the West Pomeranian region of Poland. The subjects were categorized into four subgroups (smoking and non-smoking patients with periodontal disease; smoking and non-smoking subjects without periodontal disease - control subjects). RESULTS: The differences of KIR gene frequencies between non-smoking patients and non-smoking control subjects as well as smoking patients and control subjects were not statistically significant. In multivariate regression analysis advanced age of patients and smoking were independent factors associated with increased frequency of periodontal disease. CONCLUSIONS: The results of this study suggest that the main factor associated with increased risk of periodontal disease is smoking, whereas KIR presence/absence polymorphism is not a significant factor involved in the pathogenesis of periodontal disease.

Association of variants in BAFF (rs9514828 and rs1041569) and BAFF-R (rs61756766) genes with the risk of chronic lymphocytic leukemia.

The B-cell activator factor (BAFF)/BAFF receptor (BAFF-R) axis seems to play an important role in the development and progression of chronic lymphocytic leukemia (CLL). Here, we investigated the association of eight single nucleotide polymorphisms (SNPs) in the BAFF (TNFSF13B) and BAFF-R (TNFRSF13C) genes with risk of sporadic CLL in a group of 439 CLL patients and 477 controls. We also examined the correlation between selected SNPs and CLL clinical parameters as well as BAFF plasma levels and intracellular BAFF expression. Our results point to a possible association between the rs9514828 (CT vs. CC + TT; OR = 0.74; CI 95 % = 0.57; 0.97; p = 0.022) and rs1041569 (AT vs. AA + TT; OR = 0.72; CI 95 % = 0.54; 0.95; p = 0.021) of BAFF gene and rs61756766 (CC vs. CT; OR = 2.03; CI 95 % = 1.03; 3.99; p = 0.03) of BAFF-R gene and CLL risk. Additionally, we observed that homozygotes rs1041569 AA and TT had a slightly higher risk (HR = 1.12) for the need of treatment in comparison to AT heterozygotes. In conclusion, our results indicate that SNPs in BAFF and BAFF-R genes may be considered as potential CLL risk factors.

KIR2DS5 in the presence of HLA-C C2 protects against endometriosis.

Endometriosis is defined as the presence of functional endometrial tissue outside the uterine cavity. Several hypotheses have attempted to explain the etiology and pathogenesis of endometriosis. Recently, it has been suggested that a defect of the natural killer (NK) activity in the recognition and lysis of endometrial cells is one of the crucial points in the development of this disease. Natural killer cells can express killer immunoglobulin-like receptors (KIR), which recognize class I human leukocyte antigens on target cells. We asked whether polymorphisms in KIR, HLA-C, and HLA-B genes are risk factors for endometriosis. We tested 153 women with endometriosis diagnosed on the basis of laparoscopic and histological examination, and 213 control healthy women, who gave birth to at least one child. The frequency of KIR genes in patients was similar to that in controls except for KIR2DS5, which exerted a protective effect only in HLA-C C2-positive individuals. Moreover, KIR2DS5-positive women with endometriosis had 13 times lower chance that the disease would occupy the peritoneum than KIR2DS5- and KIR2DS4del-negative ones (OR = 0.077, P = 0.0061). Similarly, KIR2DS4del-positive endometriotic persons had 11 times lower chance for peritoneal disease (OR = 0.094, P < 0.001). Negative linkage disequilibrium between KIR2DS5 and KIR2DS4del indicates that these genes are mutually exclusive. Our data suggest that KIR2DS5 may be associated with protection from endometriosis, whereas KIR2DS4del seems to be associated with higher disease stages, possibly by exclusion of protective KIR2DS5.

Presence of the full-length KIR2DS4 gene reduces the chance of rheumatoid arthritis patients to respond to methotrexate treatment.

BACKGROUND: KIR genes coding for natural killer cell immunoglobulin-like receptors, KIR, influence the effector and regulatory function of NK cells as well as some subpopulations of T lymphocytes (e.g. CD4+CD28-KIR+) depending on presence of ligands (particularly HLA-C molecules). KIR-KIR ligand interaction may lead to the development of autoimmune disorders, including rheumatoid arthritis (RA). However, their role in the response of RA patients to methotrexate therapy is not known. METHODS: KIR genes and KIR-ligand (HLA-C C1/C2 allomorphs) genotyping was performed using the PCR-SSP method in 312 RA patients (179 classified as good responders and 133 as poor responders using DAS28 criteria). Thus, we evaluated the association of KIR genes and HLA-C allomorphs with the response to methotrexate (MTX) treatment. RESULTS: We observed that patients possessing the full-length KIR2DS4 (KIR2DS4f) gene had a lower chance of responding in comparison to KIR2DS4f-negative cases. This phenomenon was observed both in erosive disease (ED) and rheumatoid factor (RF) positive and in ED- and RF-negative patients. Interestingly, the observed effect of the KIR2DS4f gene was strongest in individuals possessing medium values (20-33 mm/h) of the erythrocyte sedimentation rate (ESR). Patients with high ESR values had low probability and, in contrast, patients with low ESR had a high probability of MTX response, and the presence of KIR2DS4f did not affect their outcome. Additionally, we show that the KIR2DS4f effect did not depend on the presence of either C1 or C2 allomorphs. CONCLUSION: Our results suggest that the response of RA patients with medium ESR values to MTX treatment may be dependent on the full-length KIR2DS4 gene.

Are KIR genes associated with clinical parameters in the course of periodontitis?

INTRODUCTION: Periodontitis is a common chronic inflammatory disease. It seems that natural killer (NK) cells play a role in the pathogenesis of periodontitis. KIRs are a family of inhibitory or activating receptors expressed on the surfaces of NK cells and some subpopulations of T lymphocytes. The aim of this study was to evaluate the impact of KIR genes on the pocket depth (PD) and clinical attachment loss (CAL) parameter values as markers of disease clinical course. MATERIALS AND METHODS: The patients in the study were submitted to anamnesis and to clinical and periodontal examination. The subjects (400) were categorized into two groups: periodontitis (250 including 100 with moderate and 140 with severe periodontitis) and controls (150). Both groups were divided into two subgroups: KIR gene positive (presence of KIR gene in the genome) and KIR gene negative (lack of the KIR gene in the genome). RESULTS: The mean value for CAL was more than 5 mm, and the mean value for PD was more than 4 mm in the periodontitis group. The ANOVA test performed for the control group showed that neither PD nor CAL parameters differed between particular KIR-positive and KIR-negative healthy individuals. Similar results were obtained for all subgroups of chronic periodontitis patients and periodontitis patients (moderate as well as severe): no association between KIR genes and PD or CAL parameters was found. DISCUSSIONS: The activated immune system is important in pathogenesis of periodontal disease. On the other hand, tissue damage as a response to infection could be due to activation mediated by KIR. In our study no association between either KIR genes presence or absence and PD and CAL parameters was found. Nevertheless, the impact of KIR genes on the clinical course of periodontal disease requires further investigations.

Polymorphisms in the CD6-ALCAM axis may modulate psoriasis risk and outcomes.

The fact that CD6, along with its ligand - ALCAM, plays a role in regulating T cell activation makes the genes encoding these molecules promising candidates for research in T cell-mediated diseases such as psoriasis vulgaris (PsV). Our study aimed to determine whether CD6 (rs17824933C>G, rs11230563C>T and rs12360861G>A) and ALCAM (rs6437585C>T, rs11559013G>A) polymorphisms may affect psoriasis susceptibility and severity (assessed by Psoriasis Area and Severity Index (PASI)). Moreover, the presence of HLA-C*06:02, the strongest psoriasis risk factor in the Caucasian population, was also investigated. 273 patients diagnosed with psoriasis vulgaris and 256 blood donors with no history of PsV or other dermatoses were included in this study. Genotyping of the investigated polymorphisms was carried out using the allelic discrimination method with the application of TaqMan SNP Genotyping Assays. We observed the association of rs17824933G allele with a higher psoriasis risk in HLA-C*06:02(+) individuals (CG + GG vs CC, OR = 1.87, CI95% = 1.03; 3.37, p = 0.0350). Furthermore, we found a difference in average PASI score among groups of patients divided according to the number of CD6 and ALCAM polymorphic sites with minor alleles (F2,173 = 6.159, p = 0.0026). Collectively, our findings suggest that polymorphisms of CD6-ALCAM axis genes may modulate psoriasis risk and outcomes.

Genetic differences between smokers and never-smokers with lung cancer.

Smoking is a major risk factor for lung cancer, therefore lung cancer epidemiological trends reflect the past trends of cigarette smoking to a great extent. The geographic patterns in mortality closely follow those in incidence. Although lung cancer is strongly associated with cigarette smoking, only about 15% of smokers get lung cancer, and also some never-smokers develop this malignancy. Although less frequent, lung cancer in never smokers is the seventh leading cause of cancer deaths in both sexes worldwide. Lung cancer in smokers and never-smokers differs in many aspects: in histological types, environmental factors representing a risk, and in genes associated with this disease. In this review, we will focus on the genetic differences between lung cancer in smokers versus never-smokers: gene expression, germ-line polymorphisms, gene mutations, as well as ethnic and gender differences. Finally, treatment options for smokers and never-smokers will be briefly reviewed.

Common inherited variants of PDCD1, CD274 and HAVCR2 genes differentially modulate the risk and prognosis of adenocarcinoma and squamous cell carcinoma.

BACKGROUND: To investigate the association between single nucleotide polymorphisms (SNPs) of PDCD1, CD274, and HAVCR2 genes with the risk and outcomes of non-small cell lung cancer (NSCLC) subtypes: squamous cell lung cancer (LUSC) and lung adenocarcinoma (LUAD). METHODS: TaqMan SNP genotyping assays or polymerase chain reaction-restriction fragment length polymorphism methods were used to determine genotypes of: PDCD1: rs36084323, rs7421861, rs11568821, rs2227981, rs10204525; CD274: rs822335, rs10815225, rs17718883, rs2297136, rs4742098, rs4143815; HAVCR2: rs10057302, rs1036199. Among 383 NSCLC patients, 112 were diagnosed with LUAD and 116 with LUSC. The control group consisted of 433 unrelated, cancer-free subjects. RESULTS: A CC genotype of rs4143815 and GG genotype of rs4742098 were associated with two times higher risk of developing LUSC (CC vs. GG + GC, OR = 2.31; 95% CI = 1.32, 4.06; P = 0.003; GG vs. AA + AG, OR = 2.26; 95% CI = 1.17, 4.36; P = 0.016, respectively). Moreover, rs4143815 was an independent predictor of the age at diagnosis of LUAD. The carriers of C allele were diagnosed 4.81 years later (95% CI = 1.47, 8.15; P = 0.006) than patients with the GG genotype. The rs10057302 CA genotype was an independent predictor of overall survival in LUSC (adjusted HR = 0.13; 95% CI = 0.02, 0.93; P = 0.043). NSCLC carriers of rs11568821 T allele had almost double the risk of death (adjusted HR = 2.05; 95% CI = 1.28, 3.29; P = 0.003) compared to carriers of CC genotype. CONCLUSIONS: Our results provided additional evidence that SNPs of genes for PD-1, PD-L1 and TIM-3 differentially modulate the risk and prognosis of LUSC and LUAD.

To Be or Not to Be: The Case of Endoplasmic Reticulum Aminopeptidase 2.

To be, or not to be, that is the question. (William Shakespeare, Hamlet) Endoplasmic reticulum aminopeptidases 1 and 2 (ERAP1 and ERAP2, respectively) play a role in trimming peptides that are too long to be bound and presented by class I HLA (HLA-I) molecules to CD8+ T cells. They may also affect the HLA-I-presented peptide repertoire by overtrimming potential epitopes. Both enzymes may also be released from the cell to cleave cytokine receptors and regulate blood pressure. Both enzymes are polymorphic, which affects their expression, specificity, and activity, resulting in their role in diseases associated with HLA-I. In this brief review, we concentrate on ERAP2, less investigated because of its lack in laboratory mice and 25% of humans, as well as a lower polymorphism. ERAP2 was found to be associated with several diseases and to influence ERAP1 effects. It was discovered recently that the defective ERAP2 gene, not encoding functional aminopeptidase, may nevertheless, during viral infections, produce a truncated protein isoform of unknown function, possibly interfering with ERAP1 and full-length ERAP2 by heterodimer formation. The disease associations of ERAP2, alone or in combination with ERAP1, are reviewed.

Clinical Factors and the Outcome of Treatment with Methotrexate in Rheumatoid Arthritis: Role of Rheumatoid Factor, Erosive Disease and High Level of Erythrocyte Sedimentation Rate.

To identify the clinical factors predicting the outcome of treatment with methotrexate in rheumatoid arthritis, we examined 312 patients (253 females, 59 males) with rheumatoid arthritis diagnosed according to the criteria of the American College of Rheumatology. All patients included in this analysis began treatment with a regimen of oral MTX 7.5 mg weekly, with the dosage increasing to 15 mg weekly after 4 weeks, in combination with folic acid (1 mg daily). Good responders were defined as patients who had a DAS28 of ≤2.4 at 6 months (patients with remission of disease symptoms). Poor responders were defined as patients who had a DAS28 of >2.4. In this study, we analyzed the association between clinical parameters such as sex of patients, age of patients, age at disease onset, disease duration, rheumatoid factor, anti-CCP antibodies, ESR values, presence of joints erosions, presence of extra-articular manifestations and the response to MTX in RA patients. Multivariate logistic regression analysis showed four independent factors significantly associated with good response to MTX treatment: older age at disease onset, low ESR, no erosive disease and negative RF. The results of our study suggest that a younger age at disease onset, the presence of RF, erosive disease, as well as a high level of ESR are associated with worse response to MTX therapy.

The association of BTLA gene polymorphisms with non-small lung cancer risk in smokers and never-smokers.

Introduction: Lung cancer is the predominant cause of death among cancer patients and non-small cell lung cancer (NSCLC) is the most common type. Cigarette smoking is the prevailing risk factor for NSCLC, nevertheless, this cancer is also diagnosed in never-smokers. B and T lymphocyte attenuator (BTLA) belongs to immunological checkpoints which are key regulatory molecules of the immune response. A growing body of evidence highlights the important role of BTLA in cancer. In our previous studies, we showed a significant association between BTLA gene variants and susceptibility to chronic lymphoblastic leukemia and renal cell carcinoma in the Polish population. The present study aimed to analyze the impact of BTLA polymorphic variants on the susceptibility to NSCLC and NSCLC patients' overall survival (OS). Methods: Using TaqMan probes we genotyped seven BTLA single-nucleotide polymorphisms (SNPs): rs2705511, rs1982809, rs9288952, rs9288953, rs1844089, rs11921669 and rs2633582 with the use of ViiA 7 Real-Time PCR System. Results: We found that rs1982809 within BTLA is associated with NSCLC risk, where carriers of rs1982809G allele (AG+GG genotypes) were more frequent in patients compared to controls. In subgroup analyses, we also noticed that rs1982809G carriers are significantly overrepresented in never-smokers, but not in smokers compared to controls. Additionally, the global distribution of the haplotypes differed between the never-smokers and smokers, where haplotypes A G G C A, C G A C G, and C G A T G were more frequent in never-smoking patients. Furthermore, the presence rs1982809G (AG+GG genotypes) allele as well as the presence of rs9288953T allele (CT+TT genotypes) increased NSCLC risk in females' patients. After stratification by histological type, we noticed that rs1982809G and rs2705511C carriers were more frequent among adenocarcinoma patients. Moreover, rs1982809G and rs2705511C correlated with the more advanced stages of NSCLC (stage II and III), but not with stage IV. Furthermore, we showed that rs2705511 and rs1982809 significantly modified OS, while rs9288952 tend to be associated with patients' survival. Conclusion: Our results indicate that BTLA polymorphic variants may be considered low penetrating risk factors for NSCLC especially in never-smokers, and in females, and are associated with OS of NSCLC patients.

Weak association of anti-sperm antibodies and strong association of familial cryptorchidism/infertility with HLA-DRB1 polymorphisms in prepubertal Ukrainian boys.

BACKGROUND: Cryptorchidism is a frequent syndrome occurring in 1-2% of males within the first year of age. Autoimmune reactions, particularly directed to testicular elements and/or spermatozoa have been found to be often associated with cryptorchidism. Therefore we investigated in this study the frequency of HLA class II alleles in order to recognize possible genetic predisposition for antisperm antibodies development in prepubertal boys with diagnosed cryptorchidism in Caucasoid population. METHODS: Sixty prepubertal boys with cryptorchidism and sixty healthy boys were examined for anti-sperm antibodies by indirect immunobead test as well as for their HLA-DRB1 and -DQB1 alleles using DNA obtained from peripheral blood leukocytes. The typing of HLA-DRB1 and -DQB1 was performed by using PCR-SSP low resolution method. RESULTS: Allele frequencies of HLA-DRB1 and HLA-DQB1 did not differ between boys with cryptorchidism and control boys. However, weakly significant differences in DRB1*04 (p corrected=0.0475) and DQB1*06 (p corrected=0.0385) were seen between cryptorchid patients with and without AsA, but none of these two patient groups differed significantly in HLA class II frequencies from controls except for AsA-negatives and HLA-DQB1*06 (p corrected=0.0247). On the other hand, comparison of cryptorchid boys with familial cryptorchidism and/or infertility to control boys revealed highly significant (p corrected=0.0006) difference in HLA-DRB*11 frequency, whereas boys with sporadic cryptorchidism did not differ from control. A much weaker, but still significant difference in DRB*11 frequency was also observed between boys with bilateral cryptorchidism and controls (p corrected=0.037), whereas patients with unilateral cryptorchidism were not different from control in frequency of any HLA-DRB1 or -DQB1 allele tested. CONCLUSIONS: Predisposition to produce anti-sperm antibodies seems to be only weakly associated with HLA class II genes, although this question requires further study on much larger population sample. It is plausible that familial and sporadic cryptorchidism may present distinct genetic background. The same may, to lower extent, apply to bilateral and unilateral cryptorchidism.