Category: IHC-Antibodies

Immunoglobulin G is the most abundant antibody isotype found in the circulation. Human IgG4, one of four subclasses of IgG, contains a gamma 4 heavy chain and a hinge region that is shorter than that of IgG1. The two primary effector functions are activating complements and binding to the FcgR of effector cells to initiate phagocytosis. Human IgG4 accounts for less than 6 % of the total IgG serum level. IgG4-related sclerosing disease has been recognized as a systemic disease entity characterized by an elevated serum IgG4 level, sclerosing fibrosis, and diffuse lympho-plasmacytic infiltration with the presence of many IgG4-positive plasma cells. IgG4 is overexpressed in inflammatory pseudo-tumor (IPT) and under expressed in inflammatory myofibroblastic tumor (IMT). In pulmonary nodular lymphoid hyperplasia (PNLH), there are an increased number of IgG4+ plasma cells.

Ki-67 is a nuclear protein expressed in all proliferating cells, which are in active phases of cell cycle (late G1, S, G2, mitosis). Ki-67 is not detected in resting cells (G0 phase). Thus, the antibody is a general proliferation marker, especially used to assess the proliferative activity of a tumor. Different cancer types express Ki-67, including breast, prostate, lung, and colon.

B lymphocytes produce immunoglobulins consisting of two identical heavy chains and either two identical kappa light chains or lambda light chains. Normal lymphoid tissues therefore contain a mixture of B cells that express kappa and lambda light chains in a ratio of 2:1. This ratio is lost in tumors of B cell origin as they arise from one transformed cell, and thus only one type of light chain is expressed. The monoclonality of malignant lymphoma is used as diagnostic marker in detection with Kappa Light Chain antibody. This antibody labels kappa light chains of human immunoglobulins expressed by B lymphocytes and plasma cells. It may be helpful in detection of leukemia, plasmacytoma and various non-Hodgkin lymphoma. Other cells may also express kappa light chains resulting from non-specific immunoglobulin uptake. Kappa light chain antibody may be used in a panel with Lambda light chain.

 Calcium-dependent (C-type) lectins are a family of lectins which share structural homology in their high-affinity carbohydrate-binding domain. Proteins of the CLEC superfamily function in a variety of biological processes, including cell adhesion, cell-cell signaling, glycoprotein turnover, apoptosis, inflammation, and immune response to pathogens. CLEC4K/Langerin is a type II membrane associated receptor expressed exclusively by Langerhans cells, in astrocytoma, malignant ependymoma, but not in normal brain tissues. It recognizes mannose residues, induces membrane superimposition and zippering leading to formation of Birbeck granules. Defects in CLEC4K cause Birbeck granule deficiency, a condition characterized by the absence of Birbeck granules in epidermal Langerhans cells.

Melan A (A103), also known as MART-1 (melanoma antigen recognized by T-cells 1), is an important immunohistochemical marker for the diagnosis of maglignant melanoma. The protein is expressed on the surface of melanocytes and is located in normal skin, retina and nevi.

Melanoma (HMB-45) reacts against an antigen present in melanocytic tumors and is absolute specific for melanoma. The antibody stains fetal and neonatal melanocytes, junctional and blue nevus cells, and malignant melanocytes. Intradermal nevi, normal adult melanocytes, and non-melanocytic cells are negative. It does not stain tumor cells of epithelial, lymphoid, glial, or mesenchymal origin.

Myeloperoxidase is a peroxidase enzyme. This antibody detects granulocytes and monocytes in blood and precursors of granulocytes in the bone marrow. In normal tissues and in a variety of myeloproliferative disorders myeloid cells of both neutrophilic and eosinophilic types, at all stages of maturation, exhibit strong cytoplasmic reactivity for MPO. Erythroid precursors, megakaryocytes, lymphoid cells, mast cells, and plasma cells are nonreactive. MPO is not observed in the neoplastic cells of a wide variety of epithelial tumors and sarcomas. MPO is useful in differentiating between myeloid and lymphoid leukemias.

DNA mismatch repair (MMR) system consists of four major proteins called MLH1, MSH2, MSH6, and PMS2. These proteins work two by two, MLH1 with PMS2 and MSH2 with MSH6. Loss of function of one of the four proteins leads to inactivation of the MMR system, resulting in a loss of fidelity of the replication and an accumulation of mutations thereby leading to microsatellite instability (MSI). MSI is associated with hereditary nonpolyposis colorectal cancer (HNPCC, Lynch syndrome), which is characterized by the development of colorectal cancer, endometrial cancer and various other tumors at early age.

Loss of MSH2 function due to gene mutation or epigenetic changes is characterized by absence of nuclear expression in neoplastic cells, whereas intact nuclear MSH2 expression indicates normal MSH2 function and no gene mutations. MSH2 is normally expressed in most cases of sporadic colorectal cancer, loss of MSH2 expression is found in 13-40%.

Anti-MSH2 is useful in detection of MSI, especially in a panel with MSH6 (QR011), PMS2 (QR009) and MLH1 (QM003).

MUM1 is a transcriptional activator that binds to the interferon-stimulated response element (ISRE) of the MHC class I promoter as well as immunoglobulin lambda light chain enhancer, together with PU.1. It is expressed in the nuclei and cytoplasm of plasma cells, a subset of B-cells in the light zone of the germinal center, activated T-cells and a wide spectrum of related hematolymphoid neoplasms derived from these cells. This antibody is used to detect lymphoid malignancies and HodgkinÕs and Reed Sternberg cells of classic HodgkinÕs disease in combination with anti-CD30.

PRAME is a tumor-associated antigen that is preferentially expressed on the nuclei of neoplastic melanocytes. In normal tissue, expression of this cancer testis antigen is largely restricted to testis.
Anti-PRAME can be used for differential diagnosis of melanoma with diffuse positive nuclear staining versus nevi which are negative or only focally positive for PRAME. Therefore, it can be a helpful additional examination for situations in which antibodies against Hmb-45, Melan A and SOX10 do not provide sufficient information to distinguish between benign and malignant melanocytic lesions.
Clear cell sarcoma is reported to give consistently negative staining in contrast to malignant melanomas and can therefore be used for differential diagnosis between clear cell sarcoma (negative) vs. malignant melanoma (positive). Most synovial sarcomas and myxoid liposarcomas are diffusely positive for PRAME. Literature using other clones documented that PRAME is expressed not only by melanoma but also by various non melanoma neoplasms including non-small cell lung cancer (NSCLC), breast carcinoma, renal carcinoma, ovarian carcinoma, and leukemia.

Programmed Death Ligand 1 (PD-L1), also known as CD274 and B7-H1, is a transmembrane protein expressed on the surface of resting T-cells. Binding to its receptor PD-1, a T-cell immune checkpoint, T-cell activation is inhibited and autoimmune reaction is stopped. Some tumor cells use this mechanism to prevent apoptosis and obtain resistance against CD8+ T-cell mediated cell lysis. Blockade of the PD-1/PD-L1 pathway has now shown useful in therapy of multiple cancer types, causing durable tumor regressions in a substantial proportion of otherwise treatment refractory cases of melanoma, and carcinomas of e.g., lung, kidney, andurinary tract. Anti-PD-L1 is suitable to detect non-small cell lung cancer (NSCLC), gastric carcinoma or melanoma. According to literature PD-L1 is known to be expressed in 36-72% of NSCLC, 33-83% of melanoma and 15-69% of gastric cancer.

Programmed Death 1 (PD-1; CD279) is a transmembrane protein functioning as surface receptor for its ligands PD L1 and PD-L2. PD-1 is expressed mainly on activated T cells, B-cells and myeloid cells.
PD-1 is an immune checkpoint and plays a crucial role in down regulation of the immune system through inhibition of T-cell activation, which in turn reduces autoimmunity. Some tumor cells use this mechanism to prevent apoptosis by inhibiting T-cells directed to them. PD-1 is a useful marker for angioimmunoblastic lymphoma. Furthermore, increased expression of PD-1 has been found to be associated with poor prognosis in hepatocellular carcinoma and renal cell carcinoma. Treatments targeting PD-1 have shown encouraging results in breast cancer, non-small cell lung cancer (NSCLC) and melanoma.