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Immunohistochemistry

  • jadenewmanco
  • Jan 29, 2024
  • 2 min read

Immunohistochemistry (IHC) uses antibodies to identify specific antigens (markers) expressed by the cells of a tissue or blood sample to diagnose and grade cancers. Markers indicate cell type, tumour progression, possible cancer type and treatment as markers can be targeted by drugs. IHC antibodies are developed by injecting antigen into animals such as rabbits or mice, activating plasma B cells to produce antibodies, then extracted as anti-serum. Polyclonal antibodies are a collection of antibodies from different B cells which can bind multiple epitopes from the antigen. They are inexpensive to produce with high affinity, but batches vary reducing specificity. Monoclonal antibodies are produced from one B cell type, binding a single epitope which results in expensive but high specificity antibodies and consistency between batches.


Direct IHC technique uses a primary antibody labelled with a chromophore (enzyme) to bind the antigen however, the indirect technique uses a secondary labelled antibody to bind a primary antibody bound to the antigen. A colorimetric reaction can be visualised under a microscope when the antibody binds. For example, the enzyme horseradish peroxide (HRP) is used with DAB chromogen to visualise T cells expressing CD3 to diagnose T-cell lymphomas.


Lymphomas are cancers of the lymphoid tissue caused by lymphocyte mutation resulting in uncontrolled proliferation of lymphocytes and hyperplasia usually in the neck, groin or under arm where lymph nodes are located. Over 60 lymphoma types are categorised as Hodgkin or Non-Hodgkin. Hodgkin lymphomas contain abnormally large B-lymphocytes with multiple nuclei (Reed-Sternberg cells) observed using microscopy. 90% of non-Hodgkin lymphomas develop from B cells and 10% from T cells, both with no Reed-Sternberg cells (Lymphoma Action, 2021).


IHC, flow cytometry and microscopy are used to identify, diagnose and grade lymphomas. A sample of blood, bone marrow or fluid is processed to determine the presence of specific markers expressed in tumour cells. The NHS lymphoma panel (MFT, 2022) tests for the presence of the following markers: CD3, CD5, CD19, CD23, CD79b, Kappa chains, Lambda chains, FMC7, CD38 and optional markers: CD10, CD11c, CD25, CD103.


References

Lymphoma Action. (2021). Non-Hodgkin Lymphoma. Lymphoma Action. Retrieved April, 8, 2022,

MFT. (2022). Chronic lymphocytic/lymphoma panel. Manchester University NHS Foundation Trust. 

Carey, J. (2012). Immunophenotyping Utilizing 6 Color Flow Cytometry. Warde Medical Laboratory. 

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