immune-marker

CCR6 marks the T cells that patrol mucosal surfaces such as the gut and airway, and it is the usual way of picking out the Th17 type of helper cell.

CD11b is carried by most of the myeloid immune cells, and together with CD33 it is part of how myeloid-derived suppressor cells are defined: the cells that hold back a response against a tumour.

CD11c identifies dendritic cells, the cells that carry pieces of a tumour to the lymph node and show them to T cells. Without that step, a T cell never learns the cancer is there.

CD14 is how a monocyte is recognised: the circulating cell that becomes a macrophage once it enters tissue. Splitting monocytes by CD14 and CD16 is the first step in describing the myeloid side of a tumour.

CD141 marks the rare dendritic cells that are best at showing tumour material to killer T cells. The same protein, under its other name thrombomodulin, is part of how blood clotting is kept in check.

CD163 marks the macrophages that help a tumour rather than attack it. It is the usual way of counting those cells in a tumour sample, which is why it appears whenever tumour-associated macrophages are discussed.

CD1c marks one of the two main dendritic cell types. Unlike most antigen presentation, CD1 molecules show fats rather than protein fragments to T cells.

CD235a marks red blood cells. In an immune test its job is the opposite of the others: it is used to find red cells so they can be excluded, because there are far too many of them to leave in.

CD34 marks the blood-forming stem cells that a transplant is counted in, and it also stains blood vessels, which is how new vessel growth in a tumour is measured.

CD4 is the marker of helper T cells, the cells that direct an immune response rather than kill infected or cancerous cells themselves. A CD4 count is how the strength of that arm of the immune system is measured.

CD56 identifies natural killer cells, the part of the immune system that kills without needing to be taught what to look for. The same marker appears on neuroendocrine cancers, which is why it is used in diagnosis as well.

CD57 appears on immune cells that have divided many times and are near the end of their working life. It is the usual way of telling a worn-out T cell from a fresh one.

CD62L is the ticket a lymphocyte needs to get into a lymph node. Whether a T cell carries it separates the cells held in reserve from the ones already out working in tissue.

CD66b marks neutrophils, and specifically neutrophils that have been activated. It is the marker used to pick out the granulocyte-like suppressor cells that accumulate in people with advanced cancer.

CD69 appears within hours of a lymphocyte being activated, so it is the quickest way to tell that something has just woken the immune system up. It also keeps T cells inside a tissue rather than letting them drift back to the blood.

CD8 marks the T cells that kill: the ones that recognise a cancer cell and destroy it. How many CD8 cells sit inside a tumour, and where, is one of the few immune measurements that predicts how a cancer will behave.

CXCR3 is the receptor a killer T cell uses to find its way into a tumour. If the tumour is not making the signals it listens for, the T cells never arrive, which is one way a tumour stays cold.

CXCR5 is what draws immune cells into the follicles where B cells are trained. The same signal builds the lymph-node-like structures that sometimes form inside tumours and are linked to better outcomes.

HLA-DR is the display case that antigen-presenting cells use to show fragments to helper T cells. When monocytes lose it, the immune system is suppressed, which happens in advanced cancer and severe illness.