Spleen and the endocannabinoid system
Immunity: the main home of CB2.
Immunity: the main home of CB2. Where the cannabinoid receptors CB1 and CB2 sit in this region, what they do there, and what is actually known about CBD; at three levels for Everyone, Students and Experts, with sources.
Immune system and blood formationCB1 low · CB2 moderate (Human Protein Atlas)Last updated:
What's on this page?
Interactive 3D · real anatomy and real data
Where in your body are the cannabinoid receptors?
About 1.4 MB to download.
Regions
How to read it Choose a region, or tap a glowing point on the map.
- Solid light is the CB1 receptor, a ring is CB2. Each region has its own color; the color only tells regions apart.
- The strength of the light is the receptor gene level measured in human tissue (Human Protein Atlas). That is why the liver’s point is dim: a healthy liver has few receptors.
- With the layer selector above you can also see other receptors, the enzymes that make and break down endocannabinoids, and the liver enzymes that break down CBD and THC.
- Every piece of information shows its source and the type of evidence (human, animal, cell). You can change the reading level above.
- Drag to rotate. Use the + and − buttons to zoom; on a computer, Ctrl or ⌘ with the scroll wheel, on a phone, two fingers.
Spleen: RNA level of the receptor gene in human tissue (tissue consensus data). The tissue where CB2 is measured highest; tonsil (7.0) and lymph node (6.9) follow. Human Protein AtlasHuman tissue
| Receptor | Gene | RNA (nTPM) | Level |
|---|---|---|---|
| CB1 | CNR1 | 1.4 | low |
| CB2 | CNR2 | 8.4 | moderate |
What does it do there?
The second cannabinoid receptor (CB2) was identified from immune cells of the spleen. In human tissues, CB2 is 10–100 times more abundant than CB1 in immune organs; among blood cells, it is found most in B lymphocytes. Munro 1993AnimalCell / labGaliègue 1995Human tissue
Student level: terms and cell types
CB2 was cloned as a cannabinoid receptor expressed not in the brain but in macrophages of the marginal zone of the spleen. In human tissues, the CB2 gene is abundant in immune tissues, with expression levels 10–100 times those of CB1; the CB2 mRNA content of the spleen and tonsils is comparable to CB1 mRNA in the central nervous system. Order among blood cell subsets: B cells > natural killer cells >> monocytes > neutrophils > T8 > T4. Munro 1993AnimalCell / labGaliègue 1995Human tissue
Expert level: method notes and numbers
Spleen: RNA level of the receptor gene in human tissue (tissue consensus data). The tissue where CB2 is measured highest; tonsil (7.0) and lymph node (6.9) follow. Human Protein AtlasHuman tissue
Method note
Munro 1993: molecular cloning; the first identification of CB2. Galiègue 1995: high-sensitivity quantitative PCR and Northern blot in human immune cells and tissues; immunohistology on tonsil sections with anti-human CB2 IgG. HPA tissue consensus data: CB2 spleen 8.4 (the highest of all tissues), tonsil 7.0, lymph node 6.9, small intestine 3.1, bone marrow 1.3. Munro 1993AnimalCell / labGaliègue 1995Human tissueHuman Protein AtlasHuman tissue
What is known about CBD?
In the laboratory, CBD changed the activity of the CB2 receptor in the opposite direction (inverse agonist). This is a cell experiment finding; we have no guide topic on immunity in humans. Thomas 2007Cell / lab
Which receptor and enzyme genes are read in this region?
Values in this region for the genes in the map's layer selector: besides CB1 and CB2, the other targets of cannabinoids, the enzymes that make and break down endocannabinoids, and the liver enzymes that break down CBD and THC.
| Gene | What does it do? | Here | Tissue where it is read the most |
|---|---|---|---|
| Receptors | |||
| CB1 CNR1 | Cannabinoid receptor | 1.4 | cerebral cortex (18.6) |
| CB2 CNR2 | Cannabinoid receptor | 8.4 | spleen (8.4) |
| TRPV1 | Heat and chili pepper sensor · ion channel | 3.9 | liver (21.8) |
| GPR55 | Long an "orphan" receptor · in the cell membrane | 3.9 | testis (4.4) |
| PPARγ PPARG | Gene switch · in the cell nucleus | 11.0 | adipose tissue (153.2) |
| 5-HT1A HTR1A | Serotonin receptor · in the cell membrane | 0.0 | hippocampal formation (6.1) |
| TRPV2 | Relative of TRPV1 · ion channel | 23.2 | lung (29.5) |
| Endocannabinoid enzymes | |||
| NAPE-PLD NAPEPLD | Makes anandamide | 6.1 | kidney (13.9) |
| FAAH | Breaks down anandamide | 3.3 | testis (46.0) |
| DAGLα DAGLA | Makes 2-AG | 1.6 | cerebral cortex (12.3) |
| DAGLβ DAGLB | Makes 2-AG | 8.4 | adrenal gland (15.2) |
| MGL MGLL | Breaks down 2-AG | 40.5 | adipose tissue (161.3) |
| ABHD6 | Breaks down 2-AG | 33.0 | liver (60.7) |
| ABHD12 | Breaks down 2-AG | 20.5 | epididymis (125.2) |
| Enzymes that break down CBD and THC | |||
| CYP3A4 | Breaks down CBD and THC | 0.1 | liver (3,367.1) |
| CYP2C19 | Breaks down CBD | 0.0 | liver (178.0) |
| CYP2C9 | Breaks down THC | 0.3 | liver (1,607.6) |
RNA level shows how much the gene is read in this tissue; it does not directly show the amount of protein or how active an enzyme is. Human Protein Atlas (layers)Human tissue
Identifiers and citation
- Spleen
- Spleen · MeSH D013154 · UBERON 0002106 · Wikidata Q9371
- Receptors
- CB1 (CNR1, UniProt P21554) · CB2 (CNR2, UniProt P34972)
How to cite: cbd.school editorial team. Spleen and the endocannabinoid system. Endocannabinoid system 3D map, cbd.school. Last updated October 24, 2026. https://cbd.school/learn/endocannabinoid-system-map/dalak/
The body model is derived from BodyParts3D (DBCLS, CC BY 4.0) and Z-Anatomy (CC BY-SA 4.0); receptor levels from Human Protein Atlas v25 (CC BY 4.0). The map, text and downloaded images are CC BY-SA 4.0. An independent expert review has not been done yet. All licenses
Other pages of the map
Overview: what the endocannabinoid system is, the feedback brake at the synapse, CBD's targets, lesson mode, data and licenses.
Sources
Show 5 references
- Human Protein Atlas v25: tissue RNA consensus data (rna_tissue_consensus.tsv, HPA and GTEx, nTPM) and brain region data (rna_brain_region_hpa.tsv, nTPM), CNR1 (ENSG00000118432) and CNR2 (ENSG00000188822); v25.proteinatlas.org, file date November 6, 2025, downloaded October 24, 2026. Uhlén M et al. Tissue-based map of the human proteome. Science. 2015;347(6220):1260419. License CC BY 4.0. PMID 25613900 · doi:10.1126/science.1260419 Human tissue
- Munro S, Thomas KL, Abu-Shaar M. Molecular characterization of a peripheral receptor for cannabinoids. Nature. 1993;365(6441):61-5. PMID 7689702 · doi:10.1038/365061a0 AnimalCell / lab
- Galiègue S, Mary S, Marchand J et al. Expression of central and peripheral cannabinoid receptors in human immune tissues and leukocyte subpopulations. Eur J Biochem. 1995;232(1):54-61. PMID 7556170 · doi:10.1111/j.1432-1033.1995.tb20780.x Human tissue
- Thomas A, Baillie GL, Phillips AM et al. Cannabidiol displays unexpectedly high potency as an antagonist of CB1 and CB2 receptor agonists in vitro. Br J Pharmacol. 2007;150(5):613-23. PMID 17245363 · doi:10.1038/sj.bjp.0707133 Cell / lab
- Human Protein Atlas v25: tissue RNA consensus data (rna_tissue_consensus.tsv, HPA and GTEx, nTPM), the 17 genes in the map's layer selector: CNR1, CNR2, TRPV1, GPR55, PPARG, HTR1A, TRPV2, NAPEPLD, FAAH, DAGLA, DAGLB, MGLL, ABHD6, ABHD12, CYP3A4, CYP2C19, CYP2C9; v25.proteinatlas.org/download/tsv/rna_tissue_consensus.tsv.zip, downloaded October 24, 2026. Uhlén M et al. Tissue-based map of the human proteome. Science. 2015;347(6220):1260419. License CC BY 4.0. PMID 25613900 · doi:10.1126/science.1260419 Human tissue