Purification of natural antikeratin autoantibodies from normal human serum and their effect on human keratinocytes cultured in vitro

The adaptive immune response to porous regenerated keratin as a bone graft substitute in an ovine model

Reconstituted keratin is a novel bone graft material when prepared as a rigid scaffold. Understanding the immunogenicity of this material is important to determine whether this substance is a viable surgical option. Previous studies have shown no innate immune system activation in response to reconstituted keratin implants. To examine antibody-mediated immune responses to reconstituted keratin implants, bone and blood samples were taken from twelve sheep with surgically created tibial defects containing such implants. RT-PCR was used to detect mRNA of the inflammatory marker SOCS 3 in local bony tissue, and a novel immunohistochemistry assay developed to detect antikeratin antibodies in serum. Two animals were sacrificed per time-point at weeks 1, 2, 4, 6, 8 and 12. Time points for serum analysis included baseline (pre-surgery) and all other time points; mRNA analysis examined samples from all time points. No upregulation in antikeratin antibodies or SOCS 3 mRNA was observed at any time point, indicating that reconstituted keratin implants do not trigger an adaptive immune response in vivo in an ovine model. These findings provide the platform for further development of keratin implants in other mammalian models to define its immunogenic profile and safety.

Molecular mimicry between HSP 65 of Mycobacterium leprae and cytokeratin 10 of the host keratin; role in pathogenesis of leprosy

Mycobacteria are known to induce autoimmune response in the host. Anti-host keratrin antibodies (AkAbs) might be responsible for the autoimmune phenomena in leprosy patients as majority of leprosy lesions are manifested in the skin and occurrence of keratosis is not an uncommon feature. The aim of this study was to find out the level of AkAbs in leprosy patients across the spectrum and to explore its correlation with the clinical manifestation of the disease. Further, mimicking epitopes of keratin and Mycobacterium leprae components were characterized. We screened 140 leprosy patients (27 BT, 28 BL, 41 LL, 25 T1R, 19 ENL), 74 healthy controls (HC) and 3 psoriasis patients as positive control. Highest AkAbs level was observed in the psoriasis patients followed by T1R, LL, BL, ENL, TT/BT. AkAbs level was significantly (p<0.05) higher in all the groups of leprosy patients except TT/BT in comparison to HC. Significant positive correlation was found between number of lesions and level of AkAbs in leprosy patients. Highest lympho-proliferation for keratin protein was observed in T1R, followed by BL/LL, TT/BT, ENL. Lympho-proliferation was significantly (p<0.05) higher in all groups of leprosy patients except ENL in comparison to HC. Interestingly, it was noted that hyperimmunization of inbred strains of female BALB/c mice and rabbit with M. leprae soluble antigen (MLSA) induce higher level of AkAbs. The percentage of FoxP3(+) expressing Treg cells (total CD4(+)CD25(+)FoxP3(+) andCD4(+)CD25(+hi)FoxP3(+)) in splenocytes and lymph nodes of hyperimmunized mice were declined in comparison to control mice. Further, it was found that this autoimmune response can be adoptively transferred in naïve mice by splenocytes and lymph node cells as well as T cells. Comparative molecular characterization between keratin and MLSA noted a cross-reactivity/similarity between these two antigens. The cross-reactive protein of keratin was found to be in molecular weight range ≈74-51kDa and at pI 4.5 while the cross-reactive protein of MLSA was found to be in molecular weight ≈65kDa and at pI 4-4.5. Cross-reactive protein of keratin and MLSA was identified and characterized by MALDI-TOF/TOF analysis and Mascot software. It was found that the keratin (host protein) which reacted with anti-M. leprae sera is cytokeratin-10 and MLSA which reacted with anti-keratin sera is heat shock protein 65 (HSP 65). Seven B-cell epitopes of cytokeratin-10 and HSP 65 was found to be similar by multiple sequence alignment using ClustalW server and out of which 6 B-cell epitopes were found to be on the surface of HSP 65. In conclusion, our study provides evidence for the existence of molecular mimicry between cytokeratin-10 of keratin (host protein) and 65kDa HSP (groEL2) of M. leprae. Presence of heightened CMI response of leprosy patients to keratin and positive correlation of AkAbs level with number of lesions of leprosy patients showed the clinical evidence for its role in the pathogenesis in leprosy.

Effects of antikeratin 16 antibodies on the expression of Toll-like receptors 2 and 4 in keratinocytes

Innate immunity plays an important role in psoriasis. The possible role of Toll-like receptors (TLRs) in the activation of innate immunity in psoriasis remains unknown. Serum antikeratin 16 (anti-K16) autoantibody levels are raised in patients with psoriasis. The aim of this study was to investigate the effects of anti-K16 antibodies on TLR2 and TLR4 expression in keratinocytes. Keratinocytes were incubated with mouse anti-K16 monoclonal antibodies. Levels of TLR2 and TLR4 were measured by quantitative real-time PCR and flow cytometry. TLR2 mRNA level was increased by 1.73-fold, 1.60-fold and 2.52-fold at 6, 24 and 36 h after incubation, respectively. TLR4 mRNA level was increased by 3.62-fold and 2.21-fold at 12 and 36 h, respectively. TLR2 protein expression was increased by 1.73-fold on the cell membrane and 2.22-fold in cell membrane and intracytoplasmic locations. There was no change in TLR4. The results of this study indicate that anti-K16 antibodies may be a modulator of TLRs.

Innate immune modulation of keratinocytes by antikeratin 16 antibodies

BACKGROUND

Chronic inflammation of psoriatic lesions may be due to an exaggerated innate immune response. Toll-like receptors (TLRs) are expressed by keratinocytes in psoriasis. Antikeratin 16 autoantibodies (AK16 autoAbs) are increased in serum from patients with psoriasis. Whether the elevated AK16 autoAbs play a role in psoriasis by exaggerating innate immune response is still unknown.

OBJECTIVE

To prove that AK16 autoAbs are involved in psoriasis, by exaggerating the innate immune response of keratinocytes.

METHODS

Keratinocytes were incubated with mouse antikeratin 16 monoclonal antibodies (AK16 mAbs) for a given length of time. Levels of TLR2, TLR4, involucrin and nascent polypeptide-associated complex (NACA) mRNA were measured by quantitative RT-PCR. Levels of TLR2, TLR4, involucrin, NF-kappaB and actin-related protein 2 (ARP2) protein were measured by flow cytometry or Western blot. Effects of the mAbs on keratinocytes were studied using DNA synthesis and cell cycle analysis.

RESULTS

TLR2 mRNA increased 1.73-, 1.60- and 2.52-fold at 6, 24 and 36 h after incubation, respectively. TLR4 mRNA increased 3.62- and 2.21-fold after 12 and 36 h. Involucrin mRNA increased 2.33- and 2.0-fold after 12 and 36 h. NACA mRNA increased 5.93-, 3.35- and 3.54-fold after 12, 24 and 36 h. TLR2 protein increased 1.73-fold on the cell membrane and 2.22-fold on membrane plus intracytoplasm. NF-kappaB increased 2.64-fold after 6 h. Involucrin protein increased 4.5-fold, whereas Arp2 protein decreased 1.82-fold, after 36 h. The mAbs had an inhibitory effect on cultured keratinocytes.

CONCLUSION

AK16 autoAbs may be involved in the chronic inflammation of psoriasis lesions by promoting TLR expression.

Altered keratin 17 peptide ligands inhibit in vitro proliferation of keratinocytes and T cells isolated from patients with psoriasis

BACKGROUND

Identification of critical autoantigenic T-cell epitopes is key to developing antigen-based therapies for autoimmune diseases, including psoriasis. Our previous work demonstrated that 3 peptides on keratin 17 are able to stimulate peripheral blood lymphocytes of HLA-DRB1*07-positive patients with psoriasis and to serve as immunodominant T-cell epitopes.

OBJECTIVE

We sought to determine antagonistic altered peptide ligands to psoriatic T cells with a down-modulatory effect in inhibiting keratinocyte proliferation.

METHODS

Psoriatic altered peptide ligands were generated by single alanine residue substitutions at a critical T-cell receptor contact residue position. Antagonistic altered peptide ligands were identified by suppression screening of psoriatic T-cell activation and keratinocyte proliferation.

RESULTS

Altered peptide ligands 119R and 355L can inhibit psoriatic T-cell activation more effectively than other altered peptide ligands, especially 355L, with inhibition of T-cell proliferation and the secretion of interferon gamma and interleukin 2 in parallel with the up-regulation of interleukins 4 and 10 as well as transforming growth factor-beta. In coincubation assay, altered peptide ligands 119R and 355L can down-regulate the function of psoriatic T cells more effectively than wild-type epitopes solely, but less effectively than altered peptide ligands solely. In prepulse assay altered peptide ligand 119R can down-regulate the activation of psoriatic T cells more effectively than in coincubation but less effectively as compared with altered peptide ligand 119R only. Altered peptide ligand 355L was also shown to have a similar presentation. T-cell culture supernatants (1:100) from the concentrations (10 microg.mL(-1) and 100 microg.mL(-1) with 119R, 100 microg.mL(-1) with 355L) were more effective than the other ratios in inhibiting keratinocyte proliferation.

LIMITATIONS

This study had a relatively small sample size (52 patients and 48 healthy controls).

CONCLUSION

Our findings show that the altered peptide ligands 119R (VAALEEANTELEVKI) and 355L (ENRYCVQASQIQGLI) are capable of inhibiting proliferative responses of psoriatic T cells and keratinocyte proliferation in vitro, at least, with enhanced helper T cell type 2 polarization. Thus, to our knowledge, this article is the first report of the demonstration of therapeutic activity of altered peptide ligands derived from keratin 17.

Cloning and characterization of antikeratin human antibodies using a semisynthetic phage antibody library

Antikeratin autoantibodies (AK auto Abs) are very important elements of the human immune system. To improve the outcome of studies on AK auto Abs, it is necessary to generate antikeratin human monoclonal antibodies. The purpose of present study was to isolate antikeratin human monoclonal antibodies by panning a phage antibody library. A semisynthetic phage antibody library with capacity of 4.0x10(8) members was previously constructed. Panning of the library was performed against human epidermal keratin extracted from psoriatic scales. At the last round of the panning, individual colonies were grown in culture for expression of phage antibodies. Their binding activities and specificities to keratin were determined by ELISA, and positive clones were analyzed by DNA fingerprinting. The selected clones were induced with IPTG to express soluble Fab fragments, which were further characterized by ELISA, immunohistochemistry and Western blotting. Finally, DNA sequencing of the variable regions was performed. A human antibody clone which was able to express soluble Fab fragments and recognize Mr 46,000 keratin (K17) was isolated. DNA sequencing demonstrated that the VH and VL of the antibody came from the human VH1 and Vkappa2 families, respectively. We conclude that phage antibody library technology is a powerful way to generate human monoclonal antibodies. The antikeratin antibody we isolated in the present study would be useful in the research on AK auto Abs.