Immune Cell Markers

Immune cell markers are characteristic proteins expressed in different types of immune cells that enable researchers to distinguish between them. Antibodies are used in techniques such as flow cytometry or IHC to quantify the number of cells of a specific lineage, cell subtype or activation state – a technique called immunophenotyping. These approaches provide information about the state and functioning of an organism’s immune system in response to disease, inflammation or physiological states such as stress, as well as in diagnostics and treatment to track disease progression.

Myeloid Cell Markers

Myeloid cells are one of the two overarching lineages of hematopoietic cells. They give rise to essential immune components such as dendritic cells, granulocytes and macrophages, as well as non-immune blood cells such as erythrocytes. CD11b has historically been used as a marker of myeloid cells, although some myeloid populations, such as CD103+ dendritic cells, do not express CD11b.

Dendritic Cell Markers

Macrophage Markers

Monocyte Markers

Granulocyte Cell Markers

Granulocytes are myeloid cells bearing distinctive nuclei and characterized by the presence of granules in their cytoplasm, which contain enzymes that are released in response to infections and allergens. As part of the innate immune system, granulocytes fight pathogens as the first line of defense by secreting non-specific toxic substances such as oxygen radicals and enzymes. There are four main types of granulocytes: basophils, eosinophils, mast cells and neutrophils. Pan-granulocyte markers include CCR3, CD15, CD33, CD66b and IL5RA.

Basophil Markers

Eosinophil Markers

Mast Cell Markers

Neutrophil Markers

Lymphocyte Markers

As the second branch of the hematopoietic lineage, lymphocytes include essential immune cells of the adaptive immune system such as B cells and T cells, as well as innate lymphoid cells such as natural killer (NK) cells. Lymphocyte markers tend to be restricted to specific subsets rather than targeting all lymphocytes. For instance, CD3, CD4 and CD8 are well-established T cell markers, while CD19 marks B cells.

B Cell Markers

Also known as B lymphocytes, B cells are the main mediators of humoral immunity and immunological memory, using antibodies to fight pathogens. There are many different subsets of B cells depending on their stage of development and extent of activation. For instance, when naïve B cells are activated by antigens via their B cell receptors, they differentiate and proliferate into antibody-producing plasma cells or memory B cells. Each subset has distinct markers, usually on their cell surface, though CD19, CD20 and CD22 are common pan B cell markers.

Memory B Cell Markers

Plasma Cell Markers

T Cell Markers

T cells comprise several different types of lymphocyte that mediate the adaptive immune system with B cells. T cells can be characterized by expression of a T cell receptor (TCR) on their cell surface, which activates T cells following binding to a cognate antigen bound to a major histocompatibility complex molecule. After maturation in the thymus, from which they get their name, T cells continue to differentiate into one of several different specialized subsets. The main subtypes are helper T cells, marked by CD4, and cytotoxic T cells, marked by CD8.

Cytotoxic T Cell Markers

Memory T Cell Markers

Regulatory T Cell Markers

T Follicular Helper Cell Markers

T Helper Cell Markers

Innate Lymphoid Cell Markers

Innate lymphoid cells (ILCs) are a group of innate immune cells that resemble T cells in effects and heterogeneity, but lack antigen-specific receptors typical of the adaptive immune system. ILCs include cytotoxic (e.g. natural killer cells) and non-cytotoxic (e.g. ILC1-3) subsets. ILCs can be activated by a diverse range of stimuli and have a wide range of effector functions, contributing to immunity, inflammation and barrier function.