So I've been doing a bit of reading about the effect that cannabis has on the immune system and it's brought up some questions for me.

We now know that ingesting cannabis (via any ROA) leads to a massive release of myeloid-derived suppressor cells (MDSC), which serve to suppress the immune system. This has a number of applications for treating autoimmune diseases, but also apparently makes cannabis users more susceptible to infections and disease, and encourages tumor growth.

So for starters, does this have any impact on our understanding of how cannabis inhibits tumor growth? I'm confused how cannabis can slow tumor growth and yet simultaneously encourage it?

Also--what is the extent of the immunosuppresive effects caused by cannabis? Are they subtle enough that the effects could be reversed or made negligible by eating food or taking supplements known to boost the immune system?

I'm just curious what y'all make of this.

Cannabinoid receptor activation leads to massive mobilization of myeloid-derived suppressor cells with potent immunosuppressive properties

I think the effects of cannabis in cancer treatment is complex. In terms of its effect on immune cells, there is evidence to show that cannabis suppresses the migration (and thus metastasis) of monocyte-derived cells like macrophages which are co-opted by the tumor 'microenvironment'.
I believe cannabinoids can also selectively activate pro-apoptotic pathways in cancer cells, through ceramide pathways. In terms of it's effect on immune cells, as I've read around personally, it seems to depress the inflammatory (and tumor-killing) phenotype of macrophages (M1) and encourage the immunosuppressive M2-phenotype (those as I understand, these are oversimplified concepts of macrophage activation status). Because of the varied effects/pathways of cannabinoids, I can't say whether the suppression of immune surveillance 'outweighs' the other cellular anti-cancer (apoptosis-induction, anti-angiogenic) pathways of cannabis in terms of negative effects.

I've attached the paper on tumor-associated macrophages & cannabinoids. I'm sorry, I've had a couple beers and my thoughts are a bit jumbled. I will read the link you posted. Just wanted to share my understanding of it.

To me it's surprising and counter-intuitive that cannabis suppresses immune system.
Cannabis almost always helped healing and combating oncoming cold, if not the cure.
Well when withdrawing from cannabis, i can imagine the immune system is weakened.

i don't have time right now to go over the whole paper, but i did notice something;

They didn't use whole cannabis extract, only pure THC, and synthetic cannabinoids!
Much of the medicinal side-effects in cannabis come from CBD, not so much the THC.
So perhaps the other parts of cannabis work to harmonize and equalize THC effects.

Thanks for the paper, cave paintings.

I feel like the myriad of effects cannabis has are really nuanced, so while in this case it might be appearing to do one thing-elsewhere it may be doing something to mitigate certain effects. I dunno, my brain is a mess a right now and I'm no immunologist.

MaNoMaNoM, a lot of people seem to agree with you and swear that cannabis helps with colds. And stoners don't seem like they are particularly more prone to sickness or infection than most other people, so I definitely think that the effect it does have on the immune system is nuanced like I said.

In my own experience though, I generally try to avoid cannabis when I'm sick. I don't find that it makes things worse, but like if I have a cold and I try to smoke it tears up my throat and is just uncomfortable--can be useful for clearing out all the phlem and nastiness though. I've never tried oral ingestion or vaping it when I'm sick so maybe that's more useful. I've also heard some people argue that smoking while you're sick will make you sick for longer, which makes sense to me but I've never intentionally compared recovery times or anything like that.

As for getting stoned while sick, I have an experience to share.

I didn't get the chicken pox until I was nineteen. It was hell. I had a high fever and I ended up having to take antibiotics. Couldn't work for two weeks, almost lost my job.

So when I was recovering from that, maybe ten days in, I started to feel a bit better and one night wanted to smoke a little cannabis before bed. Now, the chicken pox were bad and they were everywhere including some in my mouth and throat. So yes, it hurt like hell when I first inhaled. But the ones in my throat took a very long time to heal. I was a daily smoker of cannabis back then.

It just felt like it took a lot longer to heal up after I started smoking cannabis again. For the first week and half or so I was basically bed-ridden and I simply wasn't able to toke. So it was pretty apparent when I did that it really slowed down the process.