Allele-Independent Turnover of Human Leukocyte Antigen (HLA) Class Ia Molecules

Major histocompatibility complex class I (MHCI) glycoproteins present cytosolic peptides to CD8+ T cells and regulate NK cell activity. Their heavy chains (HC) are expressed from up to three MHC gene loci (human leukocyte antigen [HLA]-A, -B, and -C in humans), whose extensive polymorphism maps predominantly to the antigen-binding groove, diversifying the bound peptide repertoire. Codominant expression of MHCI alleles is thus functionally critical, but how it is regulated is not fully understood. Here, we have examined the effect of polymorphism on the turnover rates of MHCI molecules in cell lines with functional MHCI peptide loading pathways and in monocyte-derived dendritic cells (MoDCs). Proteins were labeled biosynthetically with heavy water (2H2O), folded MHCI molecules immunoprecipitated, and tryptic digests analysed by mass spectrometry. MHCI-derived peptides were assigned to specific alleles and isotypes, and turnover rates quantified by 2H incorporation, after correcting for cell growth. MHCI turnover half-lives ranged from undetectable to a few hours, depending on cell type, activation state, donor, and MHCI isotype. However, in all settings, the turnover half-lives of alleles of the same isotype were similar. Thus, MHCI protein turnover rates appear to be allele-independent in normal human cells. We propose that this is an important feature enabling the normal function and codominant expression of MHCI alleles.

The kinetics of donor HLA class I-specific antibody absorption following a combined split liver and kidney transplant

Hyperacute rejection of a transplanted liver is rare even when the recipient has circulating donor-specific alloantibodies (DSA). There is also evidence that a transplanted liver may provide immunological protection for other organs transplanted from the same donor. We monitored the kinetics of circulating DSA in a highly sensitized recipient of a combined split liver and kidney transplant and demonstrated a reduction in antibody titres immediately after liver perfusion. The absorption of DSA was not compromised by the smaller liver mass transplanted. DSA titres remained low at 3 months post-transplant, and the recipient did not experience antibody-mediated rejection.

Association of the human leucocyte antigen region with susceptibility to Parkinson's disease

OBJECTIVE

The core pathology of Parkinson's disease (PD) is a loss of the dopaminergic neurons in the nigro-striatal pathway, but this is only part of a more widespread pathological process, the nature of which is unknown. Recent data suggest a possible role for inflammation in this disease process. The Human Leucocyte Antigen (HLA) region is one of the most important genetic susceptibility factors in many immune-mediated diseases but has not been extensively investigated in PD.

METHODS

The authors typed the HLA class II loci HLA-DRB1 and -DQB1 in 528 patients with Parkinson's disease and 3430 controls from the UK.

RESULTS

The authors observed an association of HLA-DRB1 with susceptibility to Parkinson's disease. In particular, HLA-DRB1*03 was more common in patients compared with controls.

CONCLUSIONS

These data suggest a possible role of the HLA region in susceptibility to Parkinson's disease and as such are consistent with other evidence supporting the role of an inflammatory process in the cellular loss in Parkinson's disease, especially of the nigral dopaminergic neurons.

A second major histocompatibility complex susceptibility locus for multiple sclerosis

Objective

Variation in the major histocompatibility complex (MHC) on chromosome 6p21 is known to influence susceptibility to multiple sclerosis with the strongest effect originating from the HLA-DRB1 gene in the class II region. The possibility that other genes in the MHC independently influence susceptibility to multiple sclerosis has been suggested but remains unconfirmed.

Methods

Using a combination of microsatellite, single nucleotide polymorphism, and human leukocyte antigen (HLA) typing, we screened the MHC in trio families looking for evidence of residual association above and beyond that attributable to the established DRB1*1501 risk haplotype. We then refined this analysis by extending the genotyping of classical HLA loci into independent cases and control subjects.

Results

Screening confirmed the presence of residual association and suggested that this was maximal in the region of the HLA-C gene. Extending analysis of the classical loci confirmed that this residual association is partly due to allelic heterogeneity at the HLA-DRB1 locus, but also reflects an independent effect from the HLA-C gene. Specifically, the HLA-C*05 allele, or a variant in tight linkage disequilibrium with it, appears to exert a protective effect (p = 3.3 × 10⁻⁵).

Interpretation

Variation in the HLA-C gene influences susceptibility to multiple sclerosis independently of any effect attributable to the nearby HLA-DRB1 gene. Ann Neurol 2007

Utility of HLAMatchmaker and single-antigen HLA-antibody detection beads for identification of acceptable mismatches in highly sensitized patients awaiting kidney transplantation

BACKGROUND

In highly sensitized patients (HSP) awaiting renal transplantation, accurate delineation of acceptable human leukocyte antigen (HLA) mismatches (AMM) aids identification of suitable crossmatch negative donors. Comparison of differences in polymorphic triplet amino acid sequences in antibody accessible regions of HLA may predict immunogenicity. We have examined the ability of the HLAMatchmaker computer algorithm to predict AMM determined by antibody screening using the full repertoire of single-antigen HLA-A and -B specificities.

METHODS

The HLA types of 24 HSP awaiting kidney transplantation were analyzed using HLAMatchmaker to determine the number of triplet amino acid (TAA) mismatches for each of 64 mismatched HLA-A and -B specificities. Patient sera with the highest immunoglobulin (Ig)G HLA-specific antibody reactivity were tested against the 64 individual HLA-A and -B specificities using single-antigen HLA antibody detection beads. Logistic regression analysis was performed to determine the association between AMM and the number of TAA mismatches.

RESULTS

There was a strong positive association between the number of TAA mismatches and the presence of HLA-specific antibody. HLA specificities with zero TAA mismatches were antibody positive in only 4 of 47 (9%) cases. A single TAA mismatches was sufficient to invoke an antibody response in 40 (41%) of 98 cases, increasing to 97 (87%) of 112 cases with 9 or more TAA mismatches. However, there was considerable heterogeneity between individual patients, and only 16 (67%) of the 24 HSP studied fitted the logistic regression model for TAA mismatches and HLA-specific antibody.

CONCLUSIONS

Identification of TAA mismatches using HLAMatchmaker is a helpful tool for predicting potential donors with an acceptable HLA mismatch in HSP.

Donor CD31 genotype and its association with acute graft-versus-host disease in HLA identical sibling stem cell transplantation

CD31 gene polymorphisms are implicated in the pathogenesis of graft-versus-host disease (GvHD) following haematopoietic stem cell transplantation (HST). We investigated the influence of CD31 genotype on the incidence of GvHD following HST from an human leukocyte antigen (HLA)-identical sibling donor. Donor and recipient CD31 codons 125, 563 and 670 DNA polymorphisms were determined in 85 cases of HLA identical sibling HST from two transplant centres. A correlation between CD31 genotype and acute GvHD was considered significant if observed in patients from both transplant centres independently. A strong correlation was identified between donor CD31 codon 125 genotype and the incidence of acute GvHD. Acute GvHD grades II-IV occurred in 27 of 46 (59%) recipients with a CD31 codon 125 leucine / valine heterozygous donor compared to nine of 39 (23%) recipients with a CD31 codon 125 homozygous donor (P=0.0019, relative-risk 2.45, 95% confidence interval 1.3-4.5). This correlation was significant in patients from both transplant centres (P=0.015 and P=0.019). We suggest that CD31 genotype may influence the function of donor-derived leukocytes and may be informative when there is a choice of comparable donors.

Monitoring systemic donor lymphocyte macrochimerism to aid the diagnosis of graft-versus-host disease after liver transplantation

BACKGROUND

The diagnosis of graft-versus-host disease (GvHD) after liver transplantation can be difficult because early symptoms are often nonspecific. In this study, the presence of donor lymphocyte macrochimerism in recipient peripheral blood was examined as a diagnostic aid for GvHD after cadaveric donor liver transplantation.

METHODS

Between 1996 and 2002, 33 liver transplant recipients with a clinical suspicion of GvHD (skin rash, diarrhea, pyrexia, pancytopenia, or anemia, without an obvious alternative cause) were investigated for peripheral blood donor lymphocyte macrochimerism. Donor macrochimerism was determined at the time of first clinical presentation by a low-sensitivity polymerase chain reaction (PCR) to detect donor human leukocyte antigen (HLA) alleles using genomic DNA extracted from recipient peripheral blood. Where donor HLA alleles were detected, the percentage of donor T cells was quantified by two-color flow cytometric analysis using antibodies specific for mismatched donor and recipient HLA alleles. The relationship between the presence or absence of donor lymphocyte macrochimerism and final diagnoses based on clinical and histological criteria was examined.

RESULTS

Seven of the 33 patients were PCR positive for donor HLA alleles. All had macrochimerism, with donor T lymphocyte levels ranging from 4% to 50% of circulating lymphocytes. All seven patients had normal liver function tests, skin rash, and diagnosis of GvHD histologically confirmed by skin or gut biopsies. Twenty-six patients were PCR negative, and, in 23, an alternative diagnosis was eventually established. The remaining three patients made a rapid and spontaneous recovery with no further symptoms suggestive of GvHD.

CONCLUSIONS

Donor lymphocyte macrochimerism was present in all patients in whom the diagnosis of GvHD was confirmed. In patients with symptoms consistent with GvHD and a negative PCR for donor HLA, an alternative diagnosis was eventually established or the patients recovered spontaneously. Detection of donor HLA alleles in recipient peripheral blood by PCR is a useful diagnostic tool for GvHD after liver transplantation.

"Gearing up" for summer. Quick tips and biking essentials

With any luck, at about the time this appears in print I'll be appearing on the street in my favorite part of my fitness program: bicycling. I don't claim to be an expert--my family thinks I'm Miguel Indurain because I can ride 20 miles at a time, and I think I'm Marco Pantani because I'm short, bald, and good on hills--but I've learned a fair amount in my last three years of riding. If you're an experienced rider you probably know at least as much as I do, but if you're a beginner--or beginning over after a long hiatus, as I did--then I have some suggestions for you.

Malpractice and the National Practitioner Data Bank: what OR nurses need to know

The National Practitioner Data Bank will record any payments made for any reason related to a malpractice suit in a central data bank available to a number of designated parties. Hospitals will be required to request this information to screen applicants and at least every 2 years for appointment renewals. The data bank may also be consulted by hospitals and state licensing boards as they deem necessary and by professional societies when reviewing membership applications. It is in the best interests of all malpractice defendants to insist on adequate representation of their personal, professional, and financial interests, which may necessitate insurance carriers providing each defendant with individual counsel.

Caught between law & nursing

Nursing has entered a new era. It is no longer accountable only to tribunals that measure scientific and technical accuracy. As health-care providers, nurses must also be able to document and justify risks, costs, complications, diagnostic and therapeutic choices, and any other decision made in the course of practicing their profession. Additionally, acceptance and adjustment must be made for working within the new parameters established by the law. James Laughlin said, "A fox was crossing a meadow and the sheep went running, but the fox has no interest in them. He is interested in a field mouse or a chipmunk. People also have such problems." The third parties and government agencies are looking for mice. As competent nurses, you must ensure that the fox has no interest in you.

Image synthesis from nonimaged laser-speckle patterns

We demonstrate that unspeckled images of coherently illuminated, diffuse objects can be formed from measurements of backscattered laser-speckle intensity. The theoretical basis for this imaging technique is outlined, and results of computer experiments that successfully construct images from digitally simulated laser-speckle measurements are presented.

Frey's syndrome: secondary to condylar fracture

Frey's syndrome, or gustatory sweating, is most commonly seen as a sequela of superficial parotidectomy. It can also be caused by other forms of trauma, including blunt trauma, but rarely does it occur without trauma.

Phaeohyphomycotic cyst of the skin caused by Exophiala jeanselmei

A dermosubcutaneous nodule presenting with a superficial papular vascular component occurred in a man receiving long-term prednisone therapy. The histologic findings were characteristic of a phaeohyphomycotic cyst, and a black mold, Exophiala jeanselmei, was isolated. Despite treatment with ketoconazole and local heat, the lesion persisted and was excised. The fungus could be seen in the excised tissue, but cultures were sterile. Subcutaneous phaeohyphomycosis is a relatively uncommon, but recently more frequently recognized type of opportunistic fungus infection.

Cystic metastasis from occult tonsillar primary simulating branchiogenic carcinoma: the case for tonsillectomy as a "grand biopsy"

The occult primary is a problem well known to head and neck surgeons. Less frequently discussed, but well documented, is cystic degeneration of metastatic nodes. When these conditions combine, they can suggest tumor arising in a pre-existing cervical cyst. This is a controversial condition, rare if it occurs at all, and is not to be invoked lightly.

High-resolution computed tomography of the middle ear and mastoid. Part II: Tubotympanic disease

Of more than 200 patients who underwent high-resolution computed tomography (CT) of the middle ear, the vast majority had tubotympanic disease in one of its forms: middle ear effusion, tympanosclerosis, granulation tissue, tympanic membrane retractions, or acquired cholesteatoma. The CT appearance of each of these conditions is discussed and illustrated. Emphasis is placed on the differential diagnosis of tubotympanic disease by determining dependent from nondependent soft-tissue opacity using two CT projections.