immunophenotyping
Meaning of immunophenotyping: Reading the badges on a cell surface to work out what the cell is and whether a population came from one ancestor.
Definition of immunophenotyping
Immunophenotyping is a laboratory method that identifies cells by the set of marker proteins they carry, using antibodies tagged with fluorescent dye that stick only to their own target. A machine then reads which tags each cell has collected, at a rate of thousands of cells a second. The resulting pattern reveals the cell type, its stage of maturity, and whether a population is mixed or descended from a single cell.
What are the markers?
Most are proteins sitting in the cell membrane, cataloged with CD numbers assigned in the order the international meetings agreed on them, so the number says nothing about what the protein does. Others sit inside the cell and are reached by making the membrane leaky first, which is why the older description of the method as reading surface markers alone is too narrow. No single marker names a cell. Identity comes from the combination: which proteins are present, which are absent, and how strongly each is expressed.
What questions does it answer?
| Question | What is looked for |
|---|---|
| Which type of leukemia or lymphoma | The maturation stage the abnormal cells are stuck at |
| Is the population from one ancestor | B cells all carrying one light chain type rather than a mixture |
| How is immune function holding up in HIV | The number of helper T cells carrying the CD4 marker |
| Is any disease left after treatment | Rare cells still bearing the original abnormal pattern |
| Why are red cells breaking apart | Blood cells missing their anchored surface proteins |
How is the result read?
Not as a yes or no. Normal cells occupy predictable positions when their marker readings are plotted, and the eye reading the result looks for a cluster where none belongs, or for cells wearing a combination that normal maturation never produces. Classifying leukemia and lymphoma is the best known application, and the comparison made is against the normal maturation ladder rather than against healthy cells in general. The same technique is applied well outside cancer: tracking the immune system in HIV, working up suspected immune deficiency in a child, and diagnosing a disorder in which blood cells lose their surface anchors and break down. Liquid samples go through a flow machine; a tissue block is stained with the same antibodies and read under a microscope instead.
Also known as
Used in a sentence
Immunophenotyping of the marrow aspirate confirmed an abnormal B-cell population.
Good to know
Identification rests on the combination of markers a population carries rather than on any single one, and the same method counts helper T cells in HIV and detects small numbers of surviving abnormal cells after treatment.
Word origin
Where “immunophenotyping” comes from
Immuno- comes from the Latin immunis, meaning exempt and so protected; phenotype joins the Greek phainein, to show, with typos, a stamp or type.