I’ve mentioned before that the people who use those terms in the same sentence don’t know what they’re talking about, generally.
Generally boosting your immune system also means you will contribute to inflammation.
But some kinds of immune-boosting are not as harmful and can actually reduce inflammation in the long term.
This would the case if for example if they prevent infections from making you sick or inhibit viral infections like EBV, which can lead to autoimmune disease.
Anyway, I decided to visit SBM and stir some trouble up, because they come off as arrogant to me. So I read the most recent post that came up.
Crislip says this:
Avoid any product that can “boost your immune system”
While it sounds impressive, the immune system cannot be boosted. When it is, in medicine we call it the inflammatory response, and is not without risk: stokes, heart attacks, and pulmonary emboli often occur after infections, probably as inflammation increases the rate of clot formation. 
This is very simplistic. This paragraph makes you believe there’s a 1 to 1 ratio of immune boosting and inflammation, and that’s far from the truth.
Some types of immune-boosting can be much less inflammatory than other kinds of immune boosting.
Vitamin D is a good example, but certainly not the only one, which can be considered ‘immune boosting’ and also ‘anti-inflammatory’.
This is misleading a bit, but so is Crislip’s statement. I wouldn’t say what Crislip says or mention immune boosting and anti-inflammatory in the same sentence. I’d expect more from an infectious disease professor.
Some general ideas:
- You can boost the immune in response to an infectious agent, but lower base levels of cytokines.
- You can boost ‘immune readiness’, without actually activating it.
- You can boost less harmful aspects of the immune system that also play a very significant role in preventing infection, but aren’t so damaging to the body.
- You can boost the immune system in one area, but not in others.
Vitamin D’s Anti-inflammatory role:
- Inhibits B cell proliferation
- Blocks B cell differentiation and immunoglobulin secretion
- Suppresses T cell proliferation
- Results in a shift from a Th1 to a Th2 phenotype
- Inhibits Th17 phenotype
- Induces T regulatory cells
- Decreased production of inflammatory cytokines (IL-17, IL-21)
- Increased production of anti-inflammatory cytokines such as IL-10.
- inhibits monocyte production of inflammatory cytokines such as IL-1, IL-6, IL-8, IL-12, and TNFα
- Inhibits DC differentiation and maturation with preservation of an immature phenotype as evidenced by a decreased expression of MHC class II molecules, co-stimulatory molecules, and IL12. 
Vitamin D also boosts the immune system:
- Vitamin D is crucial for T Cell activation. In this sense, it’s an immune booster. 
- Vitamin D increase CD8+ T Cells, which is important in controlling viral infections.
- Increases invariant Natural Killer T Cells.  – good for preventing an autoimmune disease, but bad for asthma. This shows that there’s no free ride.
- Increase NK cells.  ( are associated with…)
This is not a complete picture of how vitamin D is working, but it’s enough to demonstrate a point.
The overall effect of modulating the immune system in this way?
Vitamin D can help prevent the flu . It can also help prevent autoimmune disease and various types of inflammation.
I am not aware of any studies that show an increased likelihood of infection or illness.