Macrophage M1/M2 Polarization Simulator

Cytokine Microenvironment

M1 stimulus — LPS / IFN-γ 40%

M2 stimulus — IL-4 / IL-13 40%

Repolarization rate β 0.30

Simulation speed 1.0×

Population State

100%

Mean polarization P̄

0.00

Cells simulated

—

M1 — pro-inflammatory, microbicidal M0 — naive / unpolarized M2 — anti-inflammatory, tissue-repair

How it works

Each macrophage carries a continuous polarization index P ∈ [−1, +1]: P = +1 is fully M1, P = −1 is fully M2, P = 0 is the resting M0 state. This mirrors real biology — M1/M2 are the poles of a spectrum, not two discrete boxes, and a macrophage's transcriptional program shifts gradually as receptor engagement changes.

Each cell's polarization follows a first-order relaxation driven by its two opposing cytokine inputs, toward a receptor-engagement steady state, with a basal decay back to the resting phenotype:

dP/dt = k · [ S1·(1 − P) − S2·(1 + P) ] − β·P

S1 = LPS / IFN-γ signal (drives M1: TLR4 + IFNGR → NF-κB, STAT1)
S2 = IL-4 / IL-13 signal (drives M2: IL4R → STAT6)
β  = repolarization / basal decay rate toward M0
k  = fixed receptor-engagement gain

Steady state:  P* = k(S1 − S2) / [ k(S1 + S2) + β ]

M1 stimulus — LPS (bacterial endotoxin, TLR4 ligand) plus IFN-γ; classical activation toward the microbicidal, pro-inflammatory phenotype (iNOS, TNF-α, IL-12).
M2 stimulus — IL-4/IL-13, the alternative-activation signal that drives arginase-1, IL-10 and tissue-remodeling genes.
Repolarization rate β — how strongly an unstimulated cell relaxes back toward M0; higher β means the population needs stronger, sustained cytokine exposure to stay polarized, matching the reversibility of macrophage phenotype seen in vivo.
Every cell integrates its own noisy copy of this equation (receptor-density heterogeneity), so the population spreads into a real distribution rather than snapping in unison — color interpolates orange (M1) → gray (M0) → cyan (M2) from each cell's live P value, and activated cells swell slightly as they polarize.

Real-world relevance: this spectrum model underlies how tumor-associated macrophages (mostly M2-skewed, immunosuppressive), wound-healing macrophages (M1→M2 switch after the acute phase), and chronic-inflammation macrophages (stuck M1) are understood and targeted therapeutically.

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