The monoclonal antibody Mac 387 recognizes three S100 proteins in human neutrophils

Alarmins and Antitumor Immunity

PURPOSE

Alarmins are constitutively present endogenous molecules that essentially act as early warning signals for the immune system. We provide a brief overview of major alarmins and highlight their roles in tumor immunity.

METHODS

We searched PubMed up to January 10, 2016, using alarmins and/or damage-associated molecular patterns (DAMPs), as key words. We selected and reviewed articles that focused on the discovery and functions of alarmin and their roles in tumor immunity.

FINDINGS

Alarmins are essentially endogenous immunostimulatory DAMP molecules that are exposed in response to danger (eg, infection or tissue injury) as a result of degranulation, cell death, or induction. They are sensed by chemotactic receptors and pattern recognition receptors to induce immune responses by promoting the recruitment and activation of leukocytes, particularly antigen-presenting cells.

IMPLICATIONS

Accumulating data suggest that certain alarmins, High-mobility group nucleosome-binding protein 1 (HMGN1) in particular, contribute to the generation of antitumor immunity. Some alarmins can also be used as cancer biomarkers. Therefore, alarmins can potentially be applied for our fight against cancers.

SIV encephalitis lesions are composed of CD163(+) macrophages present in the central nervous system during early SIV infection and SIV-positive macrophages recruited terminally with AIDS

Macrophage recruitment to the central nervous system (CNS) during AIDS pathogenesis is poorly understood. We measured the accumulation of brain perivascular (CD163(+)) and inflammatory (MAC387(+)) macrophages in SIV-infected monkeys. Monocyte progenitors were 5-bromo-2'-deoxyuridine (BrdU) labeled in bone marrow, and CNS macrophages were labeled serially with fluorescent dextrans injected into the cisterna magna. MAC387(+) macrophages accumulated in the meninges and choroid plexus in early inflammation and in the perivascular space and SIV encephalitis (SIVE) lesions late. CD163(+) macrophages accumulated in the perivascular space and SIVE lesions with late inflammation. Most of the BrdU(+) cells were MAC387(+); however, CD163(+)BrdU(+) macrophages were present in the meninges and choroid plexus with AIDS. Most (81.6% ± 1.8%) of macrophages in SIVE lesions were present in the CNS before SIVE lesion formation. There was a 2.9-fold increase in SIVp28(+) macrophages entering the CNS late compared with those entering early (P < 0.05). The rate of CD163(+) macrophage recruitment to the CNS inversely correlated with time to death (P < 0.03) and increased with SIVE. In SIVE animals, soluble CD163 correlated with CD163(+) macrophage recruitment (P = 0.02). Most perivascular macrophages that comprise SIVE lesions and multinucleated giant cells are present in the CNS early, before SIVE lesions are formed. Most SIV-infected macrophages traffic to the CNS terminally with AIDS.

Proteomic biomarker analysis of amniotic fluid for identification of intra-amniotic inflammation

BACKGROUND

Intra-amniotic inflammation is associated with poor neonatal outcome independent of prematurity. We applied proteomic technology (SELDI: surface-enhanced laser desorption ionisation) to identify the proteomic profile of intra-amniotic inflammation.

DESIGN

One hundred and four samples of amniotic fluid were analysed. In stage 1, samples from patients with symptoms of preterm labour and known outcomes were tested to identify the characteristic profile for inflammation. We extracted the profile using a novel, stepwise logical approach comparing SELDI tracings from patients who delivered preterm and had intra-amniotic inflammation in response to infection to the tracings of patients who had symptoms of preterm labour but delivered at term. In stage 2, we applied the algorithm to samples from pregnancies whose outcomes were unknown to the investigators.

SETTING

North-American university in collaboration with Ciphergen field demonstration laboratory.

SAMPLE

One hundred and four samples of human amniotic fluid from transabdominal amniocentesis.

METHODS

SELDI (surface-enhanced laser desorption ionisation) and Mass Restricted analysis, a novel algorithm for extraction of clinical and biological relevant biomarkers from proteomic SELDI tracings.

MAIN OUTCOME MEASURE

Presence of intra-amniotic inflammation and/or infection leading to preterm birth.

RESULTS

Patients with intra-amniotic inflammation that deliver preterm have a distinctive amniotic fluid proteomic profile of three or four of the following proteins: neutrophil defensins-1 and -2, and calgranulins A and C. Based on the presence or absence of these biomarkers, we devised the mass restricted (MR) score ranging from 0 (all biomarker peaks absent) to 4 (all biomarker peaks present). In stage 1, MR score > 2 had 92.9% sensitivity (95% CI 76.5-98.9) and 91.8% specificity (95% CI 80.4-97.7) for detection of intra-amniotic inflammation. In blind testing (stage 2), MR score > 2 provided 100% specificity and sensitivity (95% CI 100-100). A MR score > 2 was associated with imminent preterm delivery.

CONCLUSION

Proteomic analysis of amniotic fluid reveals the presence of biomarkers characteristic of intrauterine inflammation. This methodology may identify the subgroup of patients that might benefit most from interventions to prevent fetal damage in utero.

S100A protein expression in the distinction between lentigo maligna and pigmented actinic keratosis

Lentigo maligna (LM), a type of malignant melanoma in situ, and pigmented actinic keratosis (PAK) may have similar clinical appearances but are different in prognosis and treatment. Diagnosis is established by skin biopsy. In certain cases, microscopic features may be very similar in both entities, making it difficult to determine whether the pigmented atypical cells are keratinocytes or melanocytes. Immunohistochemical markers can be useful for the identification of melanocytes in these cases. There are limitations to the use of some standard immunohistochemistry markers, however. S100 proteins are a varied group of proteins that are of special interest because of their dysregulated expression in neoplastic disorders. Their expression is changed during malignant transformation, progression, and/or metastasis in various cell lines and tumors, including melanomas. Our study analyzed the expression of several of the S100 protein subtypes (S100A2, S100A6, and S100A8/A9 or A12) in 38 LM cases and 44 PAK cases to define their potential value in the distinction between these entities together with their role in the development of early malignant melanoma of the skin. The results showed an upregulation of S100A2 protein in atypical keratinocytes in PAK and in normal keratinocytes adjacent to melanoma cells in LM. There was also an upregulation of S100A8/A9 or A12 protein, as detected by the antibody MAC387, in normal keratinocytes adjacent to both atypical keratinocytes and melanocytes in PAK and LM, respectively. There were statistically significant differences in the level of positive cells and in the pattern of immunoreactivity for anti-S100A2 and MAC387 in each entity, however. Moreover, the findings of our study support the notion that melanocyte-keratinocyte interactions are abnormal in both of these disease entities and may be involved in their progression.

S100A6 expression in fibrohistiocytic lesions

BACKGROUND

S100A6, an S100 calcium-binding protein, has been found in a variety of cutaneous and extracutaneous lesions including: melanocytic nevi, melanoma, some salivary gland and epithelial tumors, and malignant fibrous histiocytoma (MFH). Dermal dendrocytes (DD) in the papillary dermis of skin also express S100A6 protein. We evaluated a variety of cutaneous fibrohistiocytic lesions to determine if the immunophenotype of S100A6 positivity can be expanded to include some or all of these lesions.

METHODS

Formalin-fixed, paraffin-embedded tissues from fibrous papules (FP, 20), dermatofibromas (DF, 20), dermatofibrosarcoma protuberans (DFSP, 5), atypical fibroxanthomas (AFX, 5), oral fibromas (3), digital fibroma (1), and dermatomyofibroma (1) were evaluated with antibodies to S100A6, S100B, factor XIIIa, and MAC387 using a one-hour capillary action-based immunohistochemical procedure.

RESULTS

DD in 20/20 FP, 19/20 DF, and 4/4 fibromas stained positively with anti-S100A6 in a pattern similar to anti-factor XIIIa. No DFSP cases stained with anti-S100A6. Anti-S100A6 showed superior staining to anti-factor XIIIa in 4/5 AFX cases.

CONCLUSIONS

The immunophenotypes of some fibrohistiocytic lesions can be expanded to include S100A6 protein. With the exception of AFX, the use of anti-S100A6 does not appear to offer added benefit over anti-factor XIIIa in the differential diagnosis of fibrohistiocytic lesions.

Characterization of a B cell surface antigen with homology to the S100 protein MRP8

The S100 proteins comprise a large sub-family of the EF-hand calcium-binding proteins. Here we describe a novel monoclonal antibody recognizing a B cell surface antigen. This monoclonal antibody immunoprecipitates three proteins in the 12-18 kDa range and the smallest of these proteins has a striking homology at its amino-terminus to human MRP8, a myeloid specific member of the S100 family. Similarly to MRP8 in myeloid cells, this antigen is expressed in the cytoplasm of B cells and is secreted by LPS-induced activated B cells. This surface antigen is not B cell specific. Since MRP8 is not expressed by lymphoid cells, however, this antibody appears to recognize a new member of the S100 family.

Epidermal calprotectin in drug-induced toxic epidermal necrolysis

Calcium ions (Ca++) in excess alter cell viability. Their potential role in drug-induced toxic epidermal necrolysis (TEN) was investigated. Thirteen TEN patients were biopsied at the site of early bullous lesions and on clinically normal-looking skin at least 2 cm distant from blisters. Immunohistochemistry was applied using the mouse monoclonal antibody Mac 387 recognizing the cytosolic protein complex L1 (calprotectin). The L1 antigen is a calcium-binding protein expressed by human granulocytes, monocytes-macrophages and injured epidermis, but not by normal epidermis and other cells harboured in the skin. The majority (8/13) of TEN samples from apparently non-involved skin expressed the L1 antigen in a patch-like pattern inside the epidermis where inflammatory cells were scant or absent. As assessed by computerized image analysis of TEN bullous skin, the intensity of the L1 expression in the epidermis was not statistically correlated with the amount of the infiltrating inflammatory cells (Mac 387+ macrophages, UCLH1 + T lymphocytes and Factor XIIIa+ dendrocytes) present in the dermis and in the epidermis. Such findings suggest a key role for keratinocytes in the production of the L1 calcium-binding complex. As the L1 complex formation is a calcium-dependent process, one of the first biological events in TEN could be a dramatic increase in keratinocytes intracellular Ca++ concentration following damage by the involved drug metabolites. The ultimate toxic cell dysregulation would result from the disturbance in the intracellular Ca++ homeostasis.

The fatty acid-binding heterocomplex FA-p34 formed by S100A8 and S100A9 is the major fatty acid carrier in neutrophils and translocates from the cytosol to the membrane upon stimulation

Since no data are available concerning fatty acid (FA) transport in neutrophils we studied the presence of possible FA carriers. The kFA-p34 complex, composed of S100A8 and S100A9, has been implicated in the intracellular transport of arachidonic acid and its precursors in human keratinocytes. Here, we show that FA-p34 is the major FA carrier in human neutrophils (nFA-p34). The complex is highly expressed in resting neutrophils (2.65% of cytosolic proteins) and translocates to the membrane fraction upon stimulation with opsonized zymosan. Comparison of purified nFA-p34 with kFA-p34 shows that both complexes are composed of nearly the same subunits and possess similar binding properties for oleic acid. Densitometrical analyses of 2D gels show that n and kFA-p34 contain twice as much S100A8 and S100A9 suggesting an estimated stoichiometry of (S100A8)2S100A9. A method is described allowing to distinguish n and kFA-p34 from S100A8/S100A9 homo- and heteromer complexes that are devoid of FA-binding properties. After solvent extraction, we find by GC analysis linoleic acid as major endogenous ligand of purified kFA-p34. Our results suggest that nFA-p34, might be involved in the shuttling of unsaturated FA between the cytosol and the plasma membrane of neutrophils.

The S100 family of multipurpose calcium-binding proteins

Antibodies reactive with S100 protein are useful markers in a diagnostic immunohistochemistry laboratory dealing with cutaneous tumors. However, S100 protein is not a single protein but instead a group of S100 proteins with diverse functions. S100 proteins constitute a family of acidic calcium-binding proteins that are important in intracellular calcium metabolism. Recent evidence that some S100 proteins are secreted makes it likely that they are also involved in cell-cell interactions. The exploration of the status of the different members of the S100 family may yield not only diagnostic clues but also relevant functional information about the cells. Considerable recent progress has been made in our understanding of S100 proteins. This review surveys some of these findings that may be either directly or indirectly relevant to cutaneous pathology.

Phosphorylation of myeloid-related proteins MRP-14 and MRP-8 during human neutrophil activation

The myeloid-related proteins MRP-14 and MRP-8 and also p6, three calcium-binding proteins of the S100 family, translocate to the membrane during human neutrophil activation with stimuli known to require extracellular calcium for activity. When phorbol 12-myristate 13-acetate (PMA, an extracellular calcium-independent stimulus) is used, no translocation is observed. To characterize further the mechanisms involved in their translocation, phosphorylation of these proteins was studied. Three isoforms of MRP-14 were markedly phosphorylated in the membrane and in the cytosol upon activation with extracellular calcium-dependent stimuli, such as opsonized zymosan, the calcium ionophore A23187, N-formylmethionylleucylphenylalanine in the presence of cytochalasin B and arachidonic acid, or upon extracellular calcium-independent stimulation (PMA). In no case were p6 and a fourth, more basic isoform of MRP-14, phosphorylated. In PMA-activated cells, a phosphorylated acidic isoform of MRP-8 was detected in the cytosol only. However, phosphorylated MRP-8 represented only a small fraction of total MRP-8. Cgp 41251, an inhibitor of protein kinase C (PKC), completely inhibited the phosphorylation of MRP-8, and decreased cytosolic MRP-14 phosphorylation. To test whether phosphorylated MRP-8 could translocate, A23187, which induces translocation of the three S100 proteins, was added after PMA activation. This resulted in translocation of 18% +/- 5% of phosphorylated MRP-14 and 19% +/- 1% of only nonphosphorylated MRP-8. However, upon inhibition of PKC, translocation of MRP-14 and MRP-8 was increased up to 38% +/- 7% and 34% +/- 3% respectively. This suggests a putative role of phosphorylation and/or of PKC in the modulation of MRP-14 and MRP-8 translocation to the membrane.