H-2K molecules have two different C-termini, one of which is K-region specific

A liquid biopsy to detect multidrug resistance and disease burden in multiple myeloma

Multiple myeloma is an incurable cancer of bone marrow plasma cells, with a 5-year survival rate of 43%. Its incidence has increased by 126% since 1990. Treatment typically involves high-dose combination chemotherapy, but therapeutic response and patient survival are unpredictable and highly variable—attributed largely to the development of multidrug resistance (MDR). MDR is the simultaneous cross-resistance to a range of unrelated chemotherapeutic agents and is associated with poor prognosis and survival. Currently, no clinical procedures allow for a direct, continuous monitoring of MDR. We identified circulating large extracellular vesicles (specifically microparticles (MPs)) that can be used to monitor disease burden, disease progression and development of MDR in myeloma. These MPs differ phenotypically in the expression of four protein biomarkers: a plasma-cell marker (CD138), the MDR protein, P-glycoprotein (P-gp), the stem-cell marker (CD34); and phosphatidylserine (PS), an MP marker and mediator of cancer spread. Elevated levels of P-gp⁺ and PS⁺ MPs correlate with disease progression and treatment unresponsiveness. Furthermore, P-gp, PS and CD34 are predominantly expressed in CD138⁻ MPs in advanced disease. In particular, a dual-positive (CD138⁻P-gp⁺CD34⁺) population is elevated in aggressive/unresponsive disease. Our test provides a personalised liquid biopsy with potential to address the unmet clinical need of monitoring MDR and treatment failure in myeloma.

Antibodies to keyhole limpet hemocyanin cross-react with an epitope on the polysaccharide capsule of Cryptococcus neoformans and other carbohydrates: implications for vaccine development

Cryptococcus neoformans causes a life-threatening meningoencephalitis in AIDS patients. Mice immunized with a glycoconjugate vaccine composed of the glucuronoxylomannan (GXM) component of the cryptococcal capsular polysaccharide conjugated to tetanus toxoid produce Abs that can be either protective or nonprotective. Because nonprotective Abs block the efficacy of protective Abs, an effective vaccine must focus the Ab response on a protective epitope. Mice immunized with peptide mimetics of GXM conjugated to keyhole limpet hemocyanin (KLH) with glutaraldehyde developed Abs to GXM. However, control peptides P315 and P24 conjugated to KLH also elicited Abs to GXM. GXM-binding Abs from mice immunized with P315-KLH were inhibited by KLH treated with glutaraldehyde (KLH-g), but not by P315. Furthermore, KLH-g inhibited binding of GXM by serum of mice immunized with GXM-TT, indicating that glutaraldehyde treatment of KLH reveals an epitope(s) that cross-reacts with GXM. Vaccination with KLH-g or unmodified KLH elicited Abs to GXM, but did not confer protection against C. neoformans, suggesting the cross-reactive epitope on KLH was not protective. This was supported by the finding that 4H3, a nonprotective mAb, cross-reacted strongly with KLH-g. Sera from mice immunized with either native KLH or KLH-g cross-reacted with several other carbohydrate Ags, many of which have been conjugated to KLH for vaccine development. This study illustrates how mAbs can be used to determine the efficacy of potential vaccines, in addition to describing the complexity of using KLH and glutaraldehyde in the development of vaccines to carbohydrate Ags.

MHC class I heavy chain mRNA must exceed a threshold level for the reconstitution of cell surface expression of class I MHC complexes in cells transformed by the highly oncogenic adenovirus 12

In primary embryonal fibroblasts from transgenic mice expressing H-2(b) genes and a miniature swine class I transgene (PD1), transformation with adenovirus 12 results in suppression of assembly and cell surface expression of all class I complexes. Cell surface expression of PD1 can be recovered by transfecting the cells with peptide transporter genes. However, reconstitution of the H-2Kb gene expression requires, in addition, a 2-fold increase in the steady state level of the H-2Kb mRNA that can be attained by treatment of the cells with interferons or by transfecting them with the H-2Kb gene. A detailed analyses of the biogenesis of class I molecules has revealed the steady state expression of free class I heavy chains that are not converted into conformed complexes even when peptide transporter genes are overexpressed. The fact that class I complex assembly seems to be highly inefficient in certain cell lines might be a major in vivo obstacle for the elimination of transformed or virus-infected cells by cytotoxic T lymphocytes, especially in view of the fact that the level of class I gene transcription is often down-regulated in cancer cells and/or that assembly of class I major histocompatibility complexes can be subverted by virus-encoded proteins.

The mouse vitronectin receptor is a T cell activation antigen

In this report, we demonstrate that the T cell activation antigen, recognized by monoclonal antibody H9.2B8, is the murine homologue of the vitronectin receptor (VNR) and, thereby, we provide initial evidence that VNR is expressed on lymphoid cells. VNR is expressed on a variety of T cell lines, tumors, and Con A-activated splenocytes, but not resting T cells, and is capable of binding to the extracellular matrix proteins fibronectin, fibrinogen, and vitronectin, via the tripeptide sequence RGD. There was no evidence of novel beta chains pairing with the VNR alpha chain, as has been demonstrated in some human cells. In view of recent studies demonstrating that this molecule functions as an accessory molecule in T cell activation, the VNR may play an important role in mouse T cell functions.

H-2 class I loci determine sensitivity to MCMV in macrophages and fibroblasts

Peritoneal (PM) and bone marrow-derived (BMM) macrophages and lung fibroblasts (LF) from inbred, intra-H-2 recombinant, H-2 mutant, and hybrid mice were infected with murine cytomegalovirus (MCMV) under centrifugal enhancement. At the concentration of virus employed, peritoneal macrophages from strains carrying Kd, Kb, Dd, Ks and/or Ds, Kq and/or Dq alleles could be infected to a level of 80%-100%, as assessed by viral antigen expression or loss of Fc receptors. Cells lacking these haplotypes and carrying Kk, Kj, Dk, Dj, or Db were resistant, yielding levels of infection below 20%. The background (non-H-2) and class II genotype and the S allele did not influence the proportions of cells infected. Furthermore, sensitivity was dominant in the F1 progeny of H-2b X H-2k and H-2d X H-2k crosses, and was not compromised by the bm1, bm3, bm10, or bm14 mutations in the alpha 1 or alpha 2 regions of Kb or Db. The proportions of cells able to release infectious virus were low, but paralleled the frequencies of viral antigen expression. The class I genotype also determined susceptibility to MCMV infection in BMM and LF, although up to 35% of H-2k BMM and 46% of H-2k LF could be infected. The findings are consistent with an association between K and D antigens and a cellular receptor for MCMV on all three cell types.

Signals controlling alternative splicing of major histocompatibility complex H-2 class I pre-mRNA

The use of alternative splice acceptor sites during the removal of intron 7 in pre-mRNA splicing produces two forms of H-2Kb protein: the predominant form, derived from a transcript that has spliced at the upstream splice acceptor site for exon 8 (long exon 8), and a Kb molecule derived from a transcript that has spliced at the downstream acceptor site for exon 8 (short exon 8). We have identified a potential lariat branch point adenosine for the upstream acceptor splice site. This adenosine is found 28 bp from the splice junction and is contained in the sequence AGTGATGG. D-region genes, which use only the downstream splice site, have the sequence AGTGGTGG. We have used in vitro mutagenesis to change this A of the H-2Kb gene to G and have made the reciprocal change in H-2Dd. Elimination of this adenosine in H-2Kb alters the pattern of pre-mRNA splicing and results in a predominance of the Kb molecules with short exon 8 encoded sequences. However, the addition of an adenosine in H-2Dd is not sufficient to direct splicing to the upstream site.