@T-3 said in Thymus health:

What does "M2 mode" refer to?

Repolarization of macrophages M1 <> M2
Lymphocyte T polarization
In an (over-simplified) model, the Th1/Th2 and M1/M2 ratios (M=macrophages) can thus be used as indicators to determine whether or not the immune system is in M1/inhibitory type mode, oriented towards host defense, or in an M2/healing type mode, oriented towards the repair and replacement of lost or defective tissues with a view to maintaining host homeostasis. (Mills 2015a).
(doi: 10.3389/fimmu.2015.00059)
Vocabulary:
M stands for macrophage
Th stands for thymus. Th1 = T helper cell type 1, produced by thymus. = lymphocyte, a type of white blood cell.

There are two major types of T cells: the helper T cell and the cytotoxic T cell. As the names suggest helper T cells 'help' other cells of the immune system, whilst cytotoxic T cells kill virally infected cells and tumors.
Treg cells
Regulatory T cells, or Tregs, are white blood cells that play a key role in regulating your immune system. Tregs control your body's immune response to keep it from over-reacting to harmful invaders known as antigens. Antigens are frequently unwelcome substances that cause an immune response in your body.

Understanding macrophage cells and the balance to find between M1 & M2, inducing a TH1 or Th2 answer (by Treg cells). https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4329822/