Classical, intermediate and non-classical monocytes:

Monocytes can be classified as classical, intermediate and non-classical, based on expression of CD14 and CD16; there is a continuum between the three subtypes.

  • Classical: CD14+ CD16-
  • Non-classical: CD14dim CD16+
  • Intermediate: CD14+ CD16+

In normal circumstances, the classical subtype is dominant.

The proportions can be skewed in certain disease states, for example in inflammatory states.

  • It is important to recognize those subtypes to avoid overdiagnosing malignancy.

The following plots are from the peripheral blood of a patient with arthritis. There was monocytosis with a subset of non-classical monocytes with dim CD14 and gain of CD16 (note our panels do not contain CD14 and CD16 in the same tubes).

Classical Intermediate Nonclassical 1
Classical Intermediate Nonclassical 2
Classical Intermediate Nonclassical 3
Classical Intermediate Nonclassical 4

Reference: Mukherjee et al. Non-classical monocytes display inflammatory features: Validation in Sepsis and Systemic Lupus Erythematous. Sci. Rep. 5, 13886 (2015).

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