STEPTRACKERIMMUNOLOGY | QUICK REFERENCE | RAPID-FIRE REVIEW

Cells, Markers & Cytokines

One line for each cell, marker and cytokine that appears again and again — each row links back to the full page.

FOCUS ON
Three anchor groups: fever and acute phase = IL-1, IL-6, TNF-α (macrophages); helper subsets = Th1 (IFN-γ), Th2 (IL-4, 5, 13), Th17 (IL-17), Treg (IL-10, TGF-β, FOXP3); entry receptors = CD4 (HIV), CD21 (EBV), ICAM-1 (rhinovirus), ACE2 (SARS-CoV-2). Use the table as a quick self-test: cover the right-hand columns and recall them. Cell biology is on 1.02, markers on 1.04, cytokines on 3.05.
ITEM
IDENTITY
ONE-LINE FACT
PAGE
Neutrophil
CD16, multilobed
First responder; respiratory burst; ↑ with steroids
1.02
Macrophage
CD14, CD68
IL-1, IL-6, TNF-α, IL-12; activated by IFN-γ
1.02
Dendritic cell
MHC II, B7; Langerhans: CD1a, Birbeck
Primes naive T cells in nodes
1.02
NK cell
CD16, CD56
Kills MHC I–low cells; ADCC
1.02
Mast cell · basophil
FcεRI; KIT (CD117)
Histamine, tryptase; type I
4.01
Eosinophil
Major basic protein
Helminths, allergy; IL-5
1.02
T cell
CD3 (+ CD4 or CD8), CD28
MHC-restricted; thymus
1.03
B cell · plasma cell
CD19, CD20, CD21, CD40 · CD38, CD138
Antibody; class switch needs CD40L
3.03
Treg
CD4, CD25, FOXP3
IL-10, TGF-β; IPEX if absent
3.02
Stem cell
CD34
Harvest marker
1.04
IL-1
Macrophages (inflammasome)
Fever, endothelial activation · anakinra
3.05
IL-2
T cells
T-cell growth · basiliximab blocks receptor
3.05
IL-4 · IL-13
Th2
IgE switch · dupilumab
3.05
IL-5
Th2
Eosinophils, IgA · mepolizumab
3.05
IL-6
Macrophages
Acute-phase proteins, hepcidin · tocilizumab
3.05
IL-8
Macrophages, endothelium
Neutrophil chemotaxis
2.03
IL-10 · TGF-β
Tregs
Suppression; TGF-β fibrosis
3.05
IL-12
Macrophages, DCs
Th1, NK activation · ustekinumab
3.02
IL-17
Th17
Neutrophils, Candida defense · secukinumab
3.02
IFN-γ
Th1, NK, CD8⁺
Activates macrophages, ↑ MHC · IGRA measures it
3.05
IFN-α/β
Infected cells, pDCs
Antiviral state, ↑ MHC I
2.01
TNF-α
Macrophages, T cells
Shock, cachexia, granulomas · screen TB before blockers
7.03

Mechanism — the cytokine chain in a granuloma

Macrophage engulfs mycobacterium
→
IL-12 → Th1
→
IFN-γ → macrophage activation
→
TNF-α holds the granuloma together

Viral entry receptors

VIRUS
RECEPTOR
PAGE
HIV
CD4 + CCR5/CXCR4
EBV
CD21 (CR2)
Rhinovirus
ICAM-1
—
Parvovirus B19
P antigen
—
Rabies
Nicotinic ACh receptor
—
SARS-CoV-2
ACE2
—

How it's tested

COMMON CONFUSIONIL-12 drives Th1 differentiation; IL-2 drives T-cell proliferation; IFN-γ is the Th1 output — the three are often swapped in answer choices.
THE TRAPCD16 is on both NK cells and neutrophils; CD56 is the more NK-specific marker.
YOUR APPROACHCover the right columns and recall; any miss → open the linked page.

If you see… think…

Hot, swollen and fever → IL-1, IL-6, TNF-α
Eosinophilia → IL-5
IgE switch → IL-4
IgA switch → TGF-β (IL-5)
Neutrophil magnet → IL-8, C5a, LTB₄
Macrophage activator → IFN-γ
NK activators → IL-12, IFN-α/β
Treg marker pair → CD25 + FOXP3
Plasma cell markers → CD38, CD138
Hodgkin markers → CD15, CD30