The featured study came out of Brazil. Many of the plant species the authors cited as being good sources of (32%) as well as limonene (28%) and carvone (28%).  Hydro are natives of Brazil Dill is also a good source of α-phellandrene (32%) as well as limonene (28%) and carvone (28%).  Hydro distillation was used to extract 2% of the dry weight of dill.  Could dill extracts be good immuo modulators?
Previous posts on this website have presented evidence that γ Terpinene may be an agonist for CB1/2 and limonene an agonist of the adenosine AdA2A receptor. Seiquerira and coworkers studied the influence of phyllandrene on the immune response to carragean, a compound that activates the same tlr4 receptor that binds to lipopolysaccharide.  We turn to proteinatlas.org to get an idea of mRNA transcripts in various human immune cells.
A Brazilian study tested the anti-inflammatory properties of α-phllandrene
2.3. In vivo neutrophil migration induced by carrageenan in air pouch cavities
Air pouches were produced in six-day old rats and maintained that way by injecting more sterile air. Afterwards, sterile phosphate buffered saline or 1% carrageenan (100 μL/pouch) were injected into the air pouch: vehicle (3% Tween 80, 10 mL/kg, p.o.), α-phellandrene (50, 100, or 200 mg/kg, p.o.), or dexamethasone (0.5 mg/kg, p.o.). 4 h after the carrageenan injection into the air pouches, the animals were killed, and the air pouches were washed and cells counted.
Dexamethasone is best known nowadays as a steroid anti-inflammatory.
2.4. Carrageenan-induced peritonitis
Mice were first treated with saline (10 mL/kg, p.o.), vehicle (3% Tween 80, 10 mL/kg, p.o.), α-phellandrene (50, 100, or 200 mg/kg,p.o.), or dexamethasone (0.5 mg/kg, p.o.). After 1 h, peritonitis was induced in the mice by intraperitoneal injection of carrageenan diluted in sterile saline (500 μg/500 μL/cavity). After killing the mice, the peritoneal cavity was rinsed with 3-mL sterile saline and the cells in the rinse counted. The proinflammatory levels of TNF-α and IL-6 cytokines were also measured in the rinse.
The image of mesenteric lymph nodes was added to illustrate that the peritoneum is also a region rich in immune cells. Cytokines were also measured. 
Quoting from the materials section, α-Phellandrene attenuates the production of pro-inflammatory cytokines. The mice were pretreated with vehicle (3% tween 80 diluted in PBS, 10 mL/kg, p.o.) α-phellandrene (α-phe, 50 mg/kg, p.o.) or dexamethasone (Dex 0.5 mg/kg, p.o.) and 1 h later carrageenan was injected into the peritoneal cavity. A normal control group injected only with saline (10 mL/kg, p.o.) was added. 4 h after the carrageenan injection, the cavities were washed with heparinized PBS in order to determine the levels of TNF-α”
Fig. 3. Leukocytes rolling and adhesion are prevented by α-phellandrene.
The mice were pretreated with
- saline (10 mL/kg, p.o.)
- vehicle (3% tween 80 diluted in PBS, 10 mL/kg, p.o.)
- α-phellandrene (α-phe, 50 mg/kg, p.o.)
- dexamethasone (Dex 0.5 mg/kg, p.o.)
One hour later carrageenan was injected into the peritoneal cavity. After an additional four hours the mesenteric tissue was “exteriorized.” An ” intravital” microscopy was used to observe leucocyte adhesion and rolling count (cell/min). 
Fig. 4. α-phellandrene prevents mast cells degranulation.
Compound 48/80 is a polymer produced by the condensation of N-methyl-methyl-p-methoxyphenylamine with formaldehyde. It causes mast cell degranulation by binding to the MRGPRX2 G protein coupled receptor. Ketoefin is an H1 histamine receptor antagonist. According to the authors on Wikipedia, the H1 receptor is coupled to Gq resulting in an increase in intracellular Ca2+ The rats were pretreated with
- vehicle (3% tween 80 diluted in PBS, 10 mL/kg, p.o.)
- α-phellandrene (α-phe, 50, 100 or 200 mg/kg, p.o.)
- ketotifen (Keto, 2 mg/kg, p.o.). ***P < 0.001 vs compound 48/
- 80-incubated tissue group (One-Way ANOVA and Student Newman Keul’s test).
After two hours the animals were killed. The mesenteric tissue was excised incubated with saline or with the compound 48/80 (0.4 μg/mL) for 30 min. Compound 48/80 seems to activate Mrgprx2 PLCγ pathways, hence signalling via Gq. Likewise, the CB2 agonist JWH133 reduced mast cell degranulation in mouse skin after treatment with compound 48/80. The cartoon was taken from an mrgprx2 review in skin diseases.
In general, the Gq increase in intra cellular Ca2+ is what causes the mast cell. If degranulation. Could α-phellandrene be acting through Gαi pathways by binding to CB2? Similar results have been observed with specific CB2 agonists. [3,4] α-Phellandrene will be tentatively classified as a possibleCB2 agonist.
- Siqueira HDS, Neto BS, Sousa DP, Gomes BS, da Silva FV, Cunha FVM, Wanderley CWS, Pinheiro G, Cândido AGF, Wong DVT, Ribeiro RA, Lima-Júnior RCP, Oliveira FA. α-Phellandrene, a cyclic monoterpene, attenuates inflammatory response through neutrophil migration inhibition and mast cell degranulation. Life Sci. 2016 Sep 1;160:27-33. PMC free article
- Hajhashemi V, Abbasi N (2008) Hypolipidemic activity of Anethum graveolens in rats Phytother. Res., 22 (3) , pp. 372-375 free article
- Capozzi, A., Caissutti, D., Mattei, V., Gado, F., Martellucci, S., Longo, A., Recalchi, S., Manganelli, V., Riitano, G., Garofalo, T., Sorice, M., Manera, C., & Misasi, R. (2021). Anti-Inflammatory Activity of a CB2 Selective Cannabinoid Receptor Agonist: Signaling and Cytokines Release in Blood Mononuclear Cells. Molecules (Basel, Switzerland), 27(1), 64. PMC free article
- Jonsson KO, Persson E, Fowler CJ. The cannabinoid CB2 receptor selective agonist JWH133 reduces mast cell oedema in response to compound 48/80 in vivo but not the release of beta-hexosaminidase from skin slices in vitro. Life Sci. 2006 Jan 2;78(6):598-606