The immunoglobulin J chain is an evolutionarily co-opted chemokine.

The joining (J) chain regulates polymerization of multimeric Immunoglobulin(Ig)M and IgA, forming a disulfide bond to the C termini of their Ig heavy chains, and it controls IgM/IgA transport across mucosal epithelia. Like Ig itself and human-like adaptive immunity, J chain emerged in jawed vertebrates (gnathostomes), but its origin has remained mysterious since its discovery over 50 y ago. Here, we show unexpectedly that J chain is a member of the CXCL chemokine family. The J chain gene (JCHAIN) is linked to clustered CXCL chemokine loci in all gnathostomes except actinopterygians that lost JCHAIN. JCHAIN and most CXCL genes have four exons with the same intron phases, including the same cleavage site for the signal peptide/mature protein. The second exon of both genes encodes a CXC motif at the same position, and the lengths of exons 1 to 3 are similar. No other gene in the human secretome shares all of these characteristics. In contrast, intrachain disulfide bonds of the two proteins are completely different, likely due to modifications in J chain to direct Ig polymerization and mucosal transport. Crystal structures of CXCL8 and J chain share a conserved beta-strand core but diverge otherwise due to different intrachain disulfide bonds and extension of the J chain C terminus. Identification of this ancestral affiliation between J chain and CXCL chemokines addresses an age-old problem in immunology.

Decreased serum creatinine to cystatin C ratio is associated with low tongue pressure.

AIM: Tongue strength plays an important role in the process of food intake, and low tongue pressure has been associated with aspiration pneumonia, cognitive decline, and mortality. However, special equipment for tongue pressure measurement is uncommon in general practice. Recently, the serum creatinine-to-cystatin C (Cr/CysC) ratio has been validated as a marker of muscle volume mass. Thus, we aimed to investigate the association of the serum Cr/CysC ratio with tongue pressure in a cross-sectional study. METHODS: This single-center, cross-sectional study enrolled 73 participants (mean age, 71.7 years; men, 49.3%) who regularly attended the hospital for treatment of chronic disease. A tongue pressure of <30 kPa was defined as low tongue pressure. We evaluated the relationships between the serum Cr/CysC ratio and tongue pressure using multiple regression analysis. RESULTS: The serum Cr/CysC ratio was correlated with tongue pressure (R2 = 0.25, P < 0.0001). In multiple regression analyses adjusted for confounders including age, sex, body mass index, and serum albumin, the association remained significant (P = 0.0001). In logistic analyses, the multivariable-adjusted odds ratios of the Cr/CysC ratio for tertiles 1 and 2 compared with tertile 3 for low tongue pressure were 7.81 (95% confidence interval, 1.45-51.73) and 2.71 (95% confidence interval, 0.60-13.19), respectively. CONCLUSIONS: We demonstrated that a decreased serum Cr/CysC ratio was associated with a higher risk of low tongue pressure. Our findings suggest that this simple serum surrogate marker may be a first step toward an intervention for oral function by general practitioners. Geriatr Gerontol Int 2024; 24: 102-108.

Influence of blood pressure variations during hemodialysis on the prognosis of dialysis patients.

The prognosis of dialysis patients is poorer than that of the general population. The relationship between dialysis patients' blood pressure (BP) and mortality is controversial. We investigated the relationships between mortality and (i) pre-dialysis BP and (ii) BP variation during hemodialysis in maintenance dialysis patients.We retroactively analyzed the cases of the 284 patients on hemodialysis (mean age 68 ± 13 years old) who had been regularly followed at Kokura Daiichi Hospital, Japan in 2018. We assessed the relationship between the patients' BP components and risk of mortality over a 40-month follow-up.The patients' average systolic/diastolic BP values before dialysis in 2018 were 145 ± 18/77 ± 11, and those after dialysis were 129 ± 17/71 ± 10 mmHg. The prevalence of intradialytic hypotension was 46.8%. During an average follow-up of 35 months, 72 patients died, including from infectious diseases (n = 41), cardiovascular diseases (n = 9), malignancies (n = 5), and others (n = 17). The mortality rate was 32.7% in the pre-dialysis SBP < 140 mmHg group, 20.6% in the 140-159 mmHg group, and 22.2% in ≥ 160 mmHg group. In a multivariable-adjusted analysis, the hazard ratio for mortality in the pre-dialysis SBP < 140 mmHg group with intradialytic hypotension was significantly higher than that in the 140-159 mmHg group.In dialysis patients, pre-dialysis SBP < 140 mmHg and intradialytic hypotension posed a significantly higher risk for mortality. Our findings suggest that not only lower pre-dialysis BP, but also intradialytic hypotension is associated with poor prognosis in dialysis patients.

Analysis of shark NCR3 family genes reveals primordial features of vertebrate NKp30.

Natural killer (NK) cells play major roles in innate immunity against viruses and cancer. Natural killer receptors (NKR) expressed by NK cells recognize foreign- or self-ligands on infected and transformed cells as well as healthy cells. NKR genes are the most rapidly evolving loci in vertebrates, and it is generally difficult to detect orthologues in different taxa. The unique exception is NKp30, an activating NKR in mammals that binds to the self-ligand B7H6. The NKp30-encoding gene, NCR3, has been found in most vertebrates including sharks, the oldest vertebrates with human-type adaptive immunity. NCR3 has a special, non-rearranging VJ-type immunoglobulin superfamily (IgSF) domain that predates the emergence of the rearranging antigen receptors. Herein we show that NCR3 loci are linked to the shark major histocompatibility complex (MHC), proving NCR3's primordial association with the MHC. We identified eight subtypes of differentially expressed highly divergent shark NCR3 family genes. Using in situ hybridization, we detected one subtype, NS344823, to be expressed by predominantly single cells outside of splenic B cell zones. The expression by non-B cells was also confirmed by PCR in peripheral blood lymphocytes. Surprisingly, high expression of NS344823 was detected in the thymic cortex, demonstrating NS344823 expression in developing T cells. Finally, we show for the first time that shark T cells are found as single cells or in small clusters in the splenic red pulp, also unassociated with the large B cell follicles we previously identified.

Detection of abundant megakaryocytes in pulmonary artery blood in lung cancer patients using a microfluidic platform.

OBJECTIVES: The lung was recently re-discovered as a hematopoietic organ for platelet production in mice. However, evidence for the role of the lung in thrombopoiesis in humans is still limited. In this study, we examined megakaryocytes in the pulmonary and systemic circulation, specifically in pulmonary arterial blood (PAB), venous blood (PVB) and peripheral blood using a newly developed microfluidic platform for rare cell isolation. MATERIALS AND METHODS: We analyzed 23 lung cancer patients who underwent surgery in our institute. PAB and PVB were obtained from the resected lung immediately after surgery. Blood samples were size-selected using a filtration-based microfluidic device and enriched rare cells on glass slide specimens were stained with Papanicolaou (Pap), immunocytochemistry (ICC), and immunofluorescence (IF). Lung tissues were also analyzed by immunohistochemistry. RESULTS: Pap/ICC/IF showed the presence of abundant CD61+/cytokeratin- giant cells with a megakaryocyte lineage in PAB, but only a few in PVB. These megakaryocytes were found to consist of CD61+/CD41+ immature megakaryocytes and CD61+/CD41- mature megakaryocytes with the potential to produce platelets. These findings were confirmed by the conventional hematological analysis of blood smears stained with Giemsa. In analysis of lung cancer, CD61+ megakaryocytes were observed exclusively in the capillaries of non-cancerous tissue, whereas platelets were selectively observed in the tumor blood vessels of cancerous tissue. CONCLUSIONS: These results indicate that numerous megakaryocytes migrate from systemic bone marrows to accumulate in PAs and arrest of mature megakaryocytes in the capillaries of normal lung, suggesting the possibility that the lung plays a physiological role in the systemic thrombopoiesis in lung cancer patients.

Evidence for Ig Light Chain Isotype Exclusion in Shark B Lymphocytes Suggests Ordered Mechanisms.

Unlike most vertebrates, the shark IgL gene organization precludes secondary rearrangements that delete self-reactive VJ rearranged genes. Nurse sharks express four L chain isotypes, κ, λ, σ, and σ-2, encoded by 35 functional minigenes or clusters. The sequence of gene activation/expression and receptor editing of these isotypes have not been studied. We therefore investigated the extent of isotypic exclusion in separated B cell subpopulations. Surface Ig (sIg)κ-expressing cells, isolated with mAb LK14 that recognizes Cκ, carry predominantly nonproductive rearrangements of other L chain isotypes. Conversely, after depletion with LK14, sIgM+ cells contained largely nonproductive κ and enrichment for in-frame VJ of the others. Because some isotypic inclusion was observed at the mRNA level, expression in the BCR was examined. Functional λ mRNA was obtained, as expected, from the LK14-depleted population, but was also in sIgκ+ splenocytes. Whereas λ somatic mutants from the depleted sample displayed evidence of positive selection, the λ genes in sIgκ+ cells accumulated bystander mutations indicating a failure to express their products at the cell surface in association with the BCR H chain. In conclusion, a shark B cell expresses one L chain isotype at the surface and other isotypes as nonproductive VJ, sterile transcripts, or in-frame VJ whose products may not associate with the H chain. Based on the mRNA content found in the B cell subpopulations, an order of L chain gene activation is suggested as: σ-2 followed by κ, then σ and λ.

Blood pressure control status and relationship between salt intake and lifestyle including diet in hypertensive outpatients treated at a general hospital.

The purpose of the present study was to investigate blood pressure (BP) control and salt intake in hypertensive outpatients treated at a general hospital and to examine the relationship between their lifestyles and amount of salt intake. Subjects comprised 429 hypertensive patients (206 males, 223 females, and average age of 71 ± 11 years). We estimated 24-hour salt excretion using spot urine samples and assessed lifestyle using a self-description questionnaire. Average clinic BP and the number of antihypertensive drugs were 132 ± 11/73 ± 8 mmHg and 1.8 ± 0.9, respectively. In all subjects, average estimated salt intake was 9.2 ± 2.8 g/day and the rate of achievement of the estimated salt intake of <6 g/day was 11.2%. In patients with chronic kidney disease or cardiovascular disease, these values were 8.6 ± 2.6 g/day and 15.5%, and 9.1 ± 3.3 g/day and 18.2%, respectively. Estimated salt intake was lower in patients living alone than in those with a family. In a multivariate analysis, estimated salt intake correlated positively with body mass index and negatively with age. Among patients with an excessive salt intake (≥10 g/day), 75.2% answered that they made an effort to reduce their salt intake. The amount of food and processed food consumption correlated with estimated salt intake. In conclusion, the rate of achievement of salt restriction was low in hypertensive patients treated at a general hospital. It may be important to provide data on actual salt intake and guide salt restriction in the individual management of hypertension.

Effects of cigarette smoking on ambulatory blood pressure, heart rate, and heart rate variability in treated hypertensive patients.

We investigated the influence of cigarette smoking on the levels and circadian patterns of blood pressure (BP), heart rate (HR), and HR variability (HRV) in hypertensive patients. Sixteen hypertensive smokers (57 ± 2 years old) receiving antihypertensive treatments participated in this study. Ambulatory monitoring of BP, HR, and electrocardiograms was performed every 30 min for 24 hours on a smoking day and nonsmoking day in a randomized crossover manner. Average 24-hour BP and daytime BP were significantly higher in the smoking period than in the nonsmoking period. No significant differences were observed in nighttime BP between the two periods. Average 24-hour and daytime HR, but not nighttime HR, were also higher in the smoking period than in the nonsmoking period. The daytime high frequency (HF) component of HRV was attenuated more in the smoking period than in the nonsmoking period. No significant differences were observed in the low frequency (LF) components of HRV or LF/HF ratio between the two periods. These results demonstrated that cigarette smoking increased the daytime and average 24-hour BP and HR, and the increases observed in daytime BP and HR were associated with the attenuation of parasympathetic nerve activity.

Profiling contents of water-soluble metabolites and mineral nutrients to evaluate the effects of pesticides and organic and chemical fertilizers on tomato fruit quality.

In this study, the contents of water-soluble metabolites and mineral nutrients were measured in tomatoes cultured using organic and chemical fertilizers, with or without pesticides. Mineral nutrients and water-soluble metabolites were determined by inductively coupled plasma-atomic emission spectrometry and (1)H nuclear magnetic resonance spectrometry, respectively, and results were analysed by principal components analysis (PCA). The mineral nutrient and water-soluble metabolite profiles differed between organic and chemical fertilizer applications, which accounted for 88.0% and 55.4%, respectively, of the variation. (1)H-(13)C-hetero-nuclear single quantum coherence experiments identified aliphatic protons that contributed to the discrimination of PCA. Pesticide application had little effect on mineral nutrient content (except Fe and P), but affected the correlation between mineral nutrients and metabolites. Differences in the content of mineral nutrients and water-soluble metabolites resulting from different fertilizer and pesticide applications probably affect tomato quality.

Noncoordinate expression of J-chain and Blimp-1 define nurse shark plasma cell populations during ontogeny.

B-lymphocyte-induced maturation protein 1 (Blimp-1) is the master regulator of plasma cell development, controlling genes such as those encoding J-chain and secretory Ig heavy chain. However, some mammalian plasma cells do not express J-chain, and mammalian B1 cells secrete "natural" IgM antibodies without upregulating Blimp-1. While these results have been controversial in mammalian systems, here we describe subsets of normally occurring Blimp-1(-) antibody-secreting cells in nurse sharks, found in lymphoid tissues at all ontogenic stages. Sharks naturally produce large amounts of both pentameric (classically "19S") and monomeric (classically "7S") IgM, the latter an indicator of adaptive immunity. Consistent with the mammalian paradigm, shark Blimp-1 is expressed in splenic 7S IgM-secreting cells, though rarely detected in the J-chain(+) cells producing 19S IgM. Although IgM transcript levels are lower in J-chain(+) cells, these cells nevertheless secrete 19S IgM in the absence of Blimp-1, as demonstrated by ELISPOT and metabolic labeling. Additionally, cells in the shark BM equivalent (epigonal) are Blimp-1(-). Our data suggest that, in sharks, 19S-secreting cells and other secreting memory B cells in the epigonal are maintained for long periods without Blimp-1, but like in mammals, Blimp-1 is required for terminating the B-cell program following an adaptive immune response in the spleen.

Relationship between blood pressure control status and lifestyle in hypertensive outpatients.

OBJECTIVE: Lifestyle modification as well as combination antihypertensive therapy is necessary to achieve strict blood pressure (BP) control as advocated by the guidelines for the treatment of hypertension. The aim of this study was to investigate the status of adherence to lifestyle modifications and BP control status in hypertensive outpatients. METHODS AND PATIENTS: Subjects are 661 hypertensive outpatients who had been followed at National Kyushu Medical Center. We assessed BP control status based on the average clinic BP on two occasions. In addition, we investigated the adherence to the individual items of lifestyle modification by a questionnaire. RESULTS: Average BP was 129 ± 10/71 ± 11 mmHg and overall rate of achieving goal BP was 60.1%. Achieving rate of each target BP category was 83.3% in the elderly patients (<140/90 mmHg), 56.7% in the young/middle patients (<130/85 mmHg) and 45.5% in the patients with diabetes mellitus/chronic kidney disease/myocardial infarction (<130/80 mmHg). Adherance to each item of lifestyle modification was as follows: Patients who answered to be conscious about salt restriction was 80.9%, those with increased intake of fruits/vegetables was 79.0%, reduced intake of cholesterol/saturated fatty acids was 67.9%, presence of obesity was 37.7%, daily exercise for ≥30 min was 31.9%, habitual alcohol intake was 38.0%, habitual smoking was 9.8%. Only 22.5% of the patients had no lifestyle items to be modified. On the other hand, 19.6% of patients had more than 3 items to be modified. Subjects with more than 3 lifestyle items to be modified are more frequently found in young, male, and obese groups. CONCLUSION: We conclude that about 60% of the patients achieved goal BP by the intensive combination therapy. The lifestyle modification seems to be important especially for the young, male and obese patients.

Construction of a novel bioluminescent reporter system for investigating Shiga toxin expression of enterohemorrhagic Escherichia coli.

A novel chromosome-plasmid hybrid bioluminescent reporter system (C-P reporter system) utilizing Photorhabdus luminescens luxCDABE genes has been constructed to monitor the expression of Shiga toxin 1 (Stx1) and Shiga toxin 2 (Stx2) in enterohemorrhagic Escherichia coli (EHEC) in real time. The luxCDABE genes of P. luminescens have been cloned and divided into a luxCDAB cassette and a luxE gene. A promoter-less luxE gene introduced downstream from stx1 and from stx2 on EHEC chromosomes in single copies, and other luxCDAB genes were expressed on a multicopy number expression plasmid into the same cells. These Stx1- and Stx2-bioluminescent reporter strains expressed bioluminescence into bacteria cells when the expression of the promoter-less luxE gene was expressed in response to the promoter activity of stx1 and stx2, respectively. The expression levels of bioluminescence were identical to the production levels of Stx1 and Stx2 in the Stx1- and Stx2-bioluminescent reporter strains, and these strains produced both Stxs at the same respective levels as those of the parent EHEC strains. Using these reporter strains, we examined the profiles of Stx1 and Stx2 expression in EHEC. We found that production of both Stx1 and Stx2 in EHEC was enhanced upon contact with intestinal epithelial cells and within macrophages. However, the expression profiles between Stx1 and Stx2 in EHEC were different from each other under these conditions. Thus, these results suggested that this C-P reporter system is useful for determining the gene expression profile of bacteria.

Immunostimulating effects of a sulfated galactan from Codium fragile.

A pyruvylated sulfated galactan from Codium fragile is a highly ramified polysaccharide consisting of 3-linked, 3,6-linked, and non-reducing terminal d-galactose with pyruvate and sulfate groups; the glycan exerts anti-herpes simplex virus type 2 effects in vitro and in vivo. This particular polysaccharide was found to stimulate the production of nitric oxide by inducing iNOS at the mRNA and protein levels. In addition, the polysaccharide also induced several cytokine mRNA expressions such as IL-1beta, IL-6, IL-10 and TNF-alpha. Therefore, it appears that the sulfated galactan might possess the immunostimulating effects via activation of macrophages.

Novel nonclassical MHC class Ib genes associated with CD8 T cell development and thymic tumors.

In jawed vertebrates, the heterogeneous nonclassical MHC class Ib (class Ib) gene family encodes molecules structurally similar to classical MHC class Ia (class Ia) but with more limited tissue distribution and lower polymorphism. In mammals, class Ib gene products are involved in stress responses, malignancy and differentiation of intrathymic CD8 T cells. The frog Xenopus laevis possesses at least 20 class Ib genes (XNCs), and 9 subfamilies have been defined so far. We have characterized two novel subfamilies, XNC10 and XNC11. XNC10 is phylogenetically and structurally distinct from both class Ia and other XNC genes. Besides thymic lymphoid tumors, XNC10 is preferentially expressed by circulating T cells and thymocytes of the CD8 lineage both in adult and in larvae from the onset of thymus organogenesis. XNC11 is expressed only by thymocytes and upregulated by several thymic lymphoid tumors. These data provide the first evidence of the expression of any class Ib genes in Xenopus larvae, and suggests evolutionary relationships between certain class Ib genes, malignancy and CD8 T cell ontogeny.

Acquired fanconi syndrome with osteomalacia secondary to monoclonal gammopathy of undetermined significance.

A 60-year-old woman was admitted because of multiple bone pain. Examination revealed hypophosphatemic osteomalacia and acquired Fanconi syndrome. Further exploration revealed monoclonal gammopathy of undetermined significance (MGUS) excreting urinary Bence Jones protein (kappa light chain). Renal biopsy showed non-specific tubulointerstitial nephritis, yet neither crystalline inclusions in the cytoplasm of the tubular epithelium nor myeloma casts nor amyloid deposits were found. She was treated with supplementation by phosphate, alkali agents, and vitamin D, and responded well to the treatment symptomatically and biochemically. MGUS was observed without chemotherapy. Myeloma had not developed after 10 months follow-up.

Prevalence and lifestyle characteristics of hypertensive patients with metabolic syndrome followed at an outpatient clinic in fukuoka, Japan.

A new guideline on metabolic syndrome (MS) in Japanese was introduced in 2005. The purpose of this study was to evaluate the prevalence and lifestyle characteristics of Japanese hypertensive patients with MS. Subjects were 290 patients (mean age: 64+/-11 years) who had been followed at our hospital. The waist circumference (WC) and body mass index (BMI) were assessed. Subjects who had BMI >or=25 kg/m(2) were defined as having BMI obesity, while abdominal obesity was defined as a WC >or=85 cm in men and >or=90 cm in women, respectively. Since all patients had hypertension, the definition of MS was made when the patient had abdominal obesity plus either dyslipidemia or glucose intolerance, or both. Among the subjects, 230 patients underwent 24-h home urine collection to measure urinary salt and potassium excretions. Dietary habits were also assessed by use of a questionnaire. Mean values of BMI and WC were 24.2+/-3.4 kg/m(2) and 87.1+/-9.6 cm, respectively. Among the total subject group, 39% patients were classified as having BMI obesity, 49% as having abdominal obesity, and 27% as having MS. BMI was significantly correlated with WC both in men (r=0.86; p<0.01) and in women (r=0.79; p<0.01). More men than women belonged to the BMI obesity (46% vs. 33%, p<0.05), abdominal obesity (63% vs. 39%, p<0.01) and MS (39% vs. 18%, p<0.01) groups. There were no significant differences in blood pressure between patients with and without MS, while patients with MS needed a greater number of antihypertensive drugs than those without MS. Mean urinary salt and potassium excretions were 8.9+/-3.8 g/day and 1.9+/-0.7 g/day, respectively. Urinary salt excretion of <6 g (100 mmol of sodium)/day was achieved in 20% of the subjects. Urinary salt excretion in the patients with MS was significantly higher than that in the patients without (10.1+/-4.2 vs. 8.5+/-3.6 g/day; p<0.01). Only 16% of the patients with MS achieved salt restriction (<6 g/day). The patients with MS had a significantly greater the chance to eat out than the patients without MS. They were also less aware of the need to increase their vegetable consumption. The results suggested that MS is prevalent in Japanese hypertensive patients. Patients with MS showed higher urinary salt excretion and needed more antihypertensive drugs to manage their blood pressure. Dietary counseling focusing not only on sodium restriction but also on the need to increase fruit and vegetable consumption seems to be important.

Cloning and characterization of Xenopus beta2-microglobulin.

cDNAs for Xenopus beta2-microglobulin (beta2m), the obligatory light chain of most vertebrate Major Histocompatibility Complex (MHC) class I molecules, were isolated and ESTs were identified. Alignment of the deduced amino acid sequence to other species' beta2m showed that the overall structure is evolutionarily conserved, and phylogenetic analysis showed that the Xenopus beta2m sequence is intermediate between fish and bird/mammal beta2m. The Xenopus beta2m mRNA is expressed ubiquitously with highest expression in intestine, spleen, and thymus, correlating well with classical class Ia expression. beta2m mRNA and protein were also detected in Xenopus thymic tumor and kidney cell lines. Segregation analysis on a tetraploid Xenopus laevis family revealed two independently segregating, non-MHC-linked loci. As expected, only one locus was found in the diploid Xenopus tropicalis, strongly suggesting that the two beta2m loci in the tetraploid species were generated by genome-wide duplication, and did not undergo diploidization unlike many other MHC genes.

Long-term compliance with salt restriction in Japanese hypertensive patients.

The purpose of the present study was to investigate the long-term compliance with salt restriction in Japanese hypertensive patients. Subjects included 389 patients, 230 women and 159 men, mean age 58+/-11 years, who underwent successful 24-h home urine collection more than three times over an interval of a year. Urinary salt, potassium, and creatinine were measured. Additionally, family history, habitual alcohol intake, smoking habit, physical activities, and job status were assessed by use of a questionnaire. During the follow-up period (average 3.5 years), participants underwent urine collection 4.6 times in average. Urinary salt excretion at the last visit was significantly lower than that at the first visit (8.7+/-3.4 vs. 9.6+/-4.1 g/day; p<0.01). Urinary potassium excretion also decreased significantly during this period (from 2.0+/-0.7 to 1.9+/-0.7 g/day; p<0.05). Among the mean 4.6 urine collections, 45.2% (men 34.6%, women 52.6%) of the patients successfully achieved <6 g (100 mmol of sodium)/day of salt excretion on at least one occasion. The rate of achievement of averaged urinary salt excretion <6 g/day dropped to 10.3% (men 4.4%, women 14.3%). Only 2.3% (men 0.6%, women 3.5%) of the patients achieved <6 g/day on all occasions. There were no significant differences in age, habitual alcohol intake, smoking habit, physical activities, or job status between patients who complied with the salt-restricted diet and those who did not. Results suggest that long-term compliance with salt restriction is poor in Japanese hypertensive patients. Since no specifically defining characteristics were found in the compliant patients, repeated measurements of urinary salt excretion seem to be important to encourage salt restriction.

Two highly divergent ancient allelic lineages of the transporter associated with antigen processing (TAP) gene in Xenopus: further evidence for co-evolution among MHC class I region genes.

In the frog Xenopus, MHC class I antigen presentation and processing genes (the immunoproteasome LMP2 and LMP7 and the transporter TAP1 and TAP2) seem to be closely linked in a primordial organization. Two distinct lineages of class Ia and LMP7 loci were previously identified, thus strongly suggesting co-evolution among 'class I region' genes. We now show that the Xenopus MHC 'class I region' lies between class II and class III genes and we have isolated two distinct alleles at both the TAP1 and TAP2 loci. The alleles at each locus are remarkably divergent from each other and phylogenetic tree analysis revealed in both cases that they diverged from each other 60-100 million years ago (MYA). For lineage-frequency and linkage analysis, 25 wild-caught X. laevis and 16 X. tropicalis were examined. The two lineages were present in different frequencies for X. laevis and X. tropicalis. Nevertheless, in all cases, the LMP7, TAP1, and TAP2 lineages were found in a set comprising one of the two lineages. Furthermore, like the LMP7 lineages, the TAP lineages were detected in most Xenopus species that diverged from a common ancestor 80-100 MYA, suggesting that the 'class I region' biallelic lineages are under balancing selection.