Preformed Angiotensin II Type-1 Receptor Antibodies Are Associated With Rejection After Kidney Transplantation: A Single-Center, Cohort Study.

Antibodies against angiotensin II type-1 receptors (AT1R) have been increasingly recognized in association with rejection and poor allograft outcomes. Our goal was to define the prevalence of preformed antibodies against AT1R and evaluate the association with renal allograft outcomes in a consecutive cohort of 150 transplant recipients. IgG antibodies against AT1R were measured by enzyme-linked immunosorbent assay using cryopreserved serum samples obtained for HLA testing at the time of transplantation. Results were categorized as negative if <10 U/mL (44%), intermediate from 10 to 17 U/mL (38%), or strongly positive if >17 U/mL (18%). The presence of AT1R antibodies was inversely associated with age, dialysis status, and diabetes. We found a strong association between the presence of AT1R antibodies and acute cellular rejection using multivariate analyses, odds ratio 3.86 (95% CI, 1.03-14.47) for intermediate titers and 9.99 (95% CI, 2.6-38.4) for strongly positive titers. There was no association with HLA sensitization or C4d-positive antibody-mediated rejection. We did not observe a significant association with graft failure, allograft function, or proteinuria. Preformed AT1R antibodies are prevalent and highly associated with acute cellular rejection early after transplant, independent of anti-HLA antibodies. The presence of AT1R antibodies correlates with recipient characteristics that may denote stronger immune responses. Future studies are needed to evaluate the mechanism and causative effect of AT1R antibodies.

Characterization of a new HLA-C allele: Cw*1606.

HLA-Cw*16 is a relatively common HLA-C specificity among Caucasoids, with Cw*1601 being the most frequent allele. We report herein the identification by sequence-based typing of a new HLA-Cw*16 allele in a Spanish Caucasoid blood donor. The novel allele, designated Cw*1606, differs from Cw*1601 by two nucleotide changes at positions 361 (T to A) and 368 (A to C) in exon 3, which leads to two amino acid changes from Trp (TGG) to Arg (AGG) and from Tyr (TAT) to Ser (TCT) at codons 97 and 99 in the alpha2 domain, respectively. Sequence comparisons suggest that the new HLA-Cw*1606 variant could have arisen from an intralocus gene conversion event.

HLA-B*5130, a new HLA-B allele carrying a rare nucleotide substitution in exon 4.

We report herein the identification of a new HLA-B*51 allele in a Spanish Caucasoid organ donor. The novel allele, designated B*5130, differs from B*51011 by one nucleotide change at position 787 (A to G) in exon 4, leading to an amino acid change from Arg (AGA) to Gly (GGA) at codon 239 in the alpha3 domain. This substitution is present in most classical and nonclassical HLA class I loci (A, C, E, and G) but not in any of the HLA-B alleles reported so far, except for B*7301. Although the frequency of the new variant seems to be low, its existence makes mandatory the analysis of exon 4 before assigning a B*5101 type.

Residues Y429 and Y463 of the human CD5 are targeted by protein tyrosine kinases.

The human CD5 lymphocyte cell surface co-receptor modulates activation and differentiation responses mediated by the antigen-specific receptor of T and B cells. CD5 is phosphorylated following lymphocyte activation; however, the exact sites and kinases involved are yet to be determined. Jurkat T cell transfectants expressing tyrosine-mutated CD5 molecules have been used to show that residues Y429 and Y463 are targeted in vivo by protein tyrosine kinases following cell stimulation with anti-CD3 mAb or pervanadate. This is in agreement with data from direct in vitro kinase assays using purified recombinant Lck and Fyn protein tyrosine kinases. The analysis of Lck- and CD3-deficient Jurkat cells shows that tyrosine phosphorylation of CD5 requires Lck activity. We propose that T cell activation mediates CD5 tyrosine phosphorylation at residues Y429 and Y463 mainly through the activation of Lck.

Identification of a novel single-nucleotide polymorphism (Val554Ile) and definition of eight common alleles for human IL4RA exon 11.

The interleukin (IL)-4 receptor alpha chain gene (IL4RA) is a polymorphic gene which is reportedly involved in the development of atopy. Of the 14 single-nucleotide polymorphisms (SNP) reported to date in the coding region of IL4RA, 11 are positioned to exon 11. This big exon encodes more than two thirds of the mature protein, including most of the cytoplasmic region. Here we report the identification of a new IL4RA SNP at the first nucleotide of codon 554 (GTA --> ATA) in exon 11, leading to an amino acid substitution from Val to Ile (V554I). Furthermore, we present complete nucleotide sequence data for eight common alleles resulting from combinations of 9 out of the 12 SNP at IL4RA exon 11. Homo- or heterozygous combinations of these eight alleles accounted for all the IL4RA exon 11 genotypes found in Caucasian individuals from our geographical area.

Role of two conserved cytoplasmic threonine residues (T410 and T412) in CD5 signaling.

CD5 is a transmembrane coreceptor that modulates activation and differentiation signals mediated by the Ag-specific receptor present on both T and B1a lymphocytes. CD5 lacks intrinsic catalytic activity, and its immunomodulatory properties result from intracellular interactions mediated by the CD5 cytoplasmic tail. The nature of these interactions is currently a matter of investigation. Here, we present a selective mutagenesis analysis of two conserved threonine residues (T410 and T412) located at the membrane-proximal cytoplasmic region of CD5. These residues are contained within consensus phosphorylation motifs for protein kinase C and are shown here to be critical for in vivo protein kinase C-mediated phosphorylation of CD5. Functional studies revealed that the integrity of T410 and T412 is also critical for CD5-mediated phosphatidylcholine-specific phospholipase C (PC-PLC) activation and phorbol ester-mediated inhibition of Ab-induced internalization of CD5. These results strongly argue in favor of a role for T410 and T412 in the signaling mediated by CD5.

Genomic organization of the human CD5 gene.

CD5 is a member of the family of receptors which contain extracellular domains homologous to the type I macrophage scavenger receptor cysteine-rich (SRCR) domain. Here, we compare the exon/intron organization of the human CD5 gene with its mouse homologue, as well as with the human CD6 gene, the closest related member of the SRCR superfamily. The human CD5 gene spans about 24.5 kb and consists of at least 11 exons. These exons are conserved in size, number, and structure in the mouse CD5 homologue. No evidence for the biallelic polymorphism reported in the mouse could be found among a population of 100 individuals of different ethnic origins. The human CD5 gene maps to the Chromosome (Chr) 11q12.2 region, 82 kb downstream from the human CD6 gene, in a head-to-tail orientation, a situation which recalls that reported at mouse Chr 19. The exon/intron organization of the human CD5 and CD6 genes was very similar, differing in the size of intron 1 and the number of exons coding for their cytoplasmic regions. While several isoforms, resulting from alternative splicing of the cytoplasmic exons, have been reported for CD6, we only found evidence of a cytoplasmic tailless CD5 isoform. The conserved structure of the CD5 and CD6 loci, both in mouse and human genomes, supports the notion that the two genes may have evolved from duplication of a primordial gene. The existence of a gene complex for the SRCR superfamily on human Chr 11q (and mouse Chr 19) still remains to be disclosed.

The scavenger receptor cysteine-rich superfamily (SRCR-SF). Structure and function of group B members / The scavenger receptor cysteine-rich superfamily (SRCR-SF). Structure and function of group B members

La recientemente descrita superfamilia de receptores con dominios extracelulares ricos en cisteína tipo scavenger (SF-SRCR) incluye un grupo diverso de algo más de 20 proteínas integrales de membrana y/o secretadas pre s e n t e s en un amplio espectro de especies animales (desde los invertebrados más primitivos hasta los mamíferos más evolucionados). Sus miembros se caracterizan por la presencia de uno o múltiples dominios ricos en cisteína denominados SRCR (Scavenger Receptor Cysteine-Rich), que fueron identificados por vez primera en el receptor scavenger tipo I de los macrófagos (SR-AI). Estos dominios SRCR tienen aproximadamente 110 residuos y poseen 6 ó 8 cisteínas (dependiendo de si pertenecen al grupo A ó B, respectivamente) que forman puentes disulfuro con una distribución intradominio muy bien definida. A pesar de la presencia de estos dominios altamente conservados, los miembros de la SF-SRCR parecen poseer ligandos y funciones diferentes. No obstante, la mayoría están expresados en células asociadas con funciones de reconocimiento o de defensa por lo que se piensa que el papel principal de la SF-SRCR es el de regular el desarrollo y la función del Sistema Inmunitario, tanto innato como específico. En este trabajo pasamos revista a los conocimientos actuales sobre la estructura y la función de los 9 miembros conocidos del grupo B de la SF-SRCR. Este heterogéneo grupo incluye moléculas expresadas en linfocitos (CD5, CD6, T19/WC1) y macrófagos (M130/CD163, Sp /AIM) de mamíferos, así como en órganos no linfoides de mamíferos (CRP-ductin/DMBT1/Ebnerin/Hensin, Gall-gladder mucin) y otras especies inferiores (Pema-SREG, MAP-GEOCY) (AU)

Identification of a novel HLA-Cw*07 variant (Cw*0714) in a German Caucasian family.

We report herein the identification of a new HLA-Cw*07 allele in two members of a German Caucasian family. This novel allele, designated as Cw*0714, differs from Cw*07011 and Cw*0706 by two nucleotide changes: one at codon 66 (AAC-->AAG) in the exon 2, leading to an amino acid change from Asn to Lys; and another silent substitution at codon 99 (TAT-->TAC) in the exon 3. The latest substitution (T-->C at the third position of codon 99) was not seen in any of the HLA-Cw*07 alleles reported so far, thus being characteristic to the new HLA-Cw*0714 allele.