Yes, this mutation can cause a person to have lowered immunity, and also can cause a person to have difficulty detoxifying during herxheimer reactions.
Compensation is easy, though (relatively)... Requires avoidance of folic acid as much as you can (usually only found in pills and fortified foods such as bread or cereal), and instead take a supplement of methylfolate (5-methyltetrahydrofolate) and also need Vitamin B12 - preferrably the hydroxy-B12 or methyl-B12 and not cyano-B12.
Start with small doses of the methylfolate, because when you first begin to compensate for this MTHFR mutation (which causes an inability to convert Folic Acid to methylfolate, thus stopping the production of glutathione), all the stored up toxins can suddenly start to get released...
This causes a toxicity reaction that can be a bit uncomfortable... thus the need to start slowly and then slowly increase.
Other supporting supplements include:
B-Complex (specifically, the active forms of the B vitamins, such as methyl-B12, methylfolate, P5P, etc.)
Iron (if deficient; don't take supplemental iron if not deficient)
Vitamins D, A, E
Other antioxidants (pycnogenol, etc.)
And may also need to support the liver with Milk Thistle.
Also, if one has sulfur/sulfite sensitivity, it is likely there are other methylation cycle genomic variants (mutations) that need to be dealt with prior to initiating support for the MTHFR mutation.
The only test I know of that looks at all the mutations is Dr. Yasko's Comprehensive Methylation Panel. See www.holisticheal.com/
for more info.
Chronic Lyme, Bart., Gluten & Sulfite Sensitivity, Many Food/Inhalant/Medication/Chemical Allergies & Intolerances, Asthma, Gut dysmotility & non-specific inflammation, Lupus, Osteoporosis, etc.; G-Tube
Meds: Flagyl, Domperidone, Claritin, Andrographis & other herbs, homeopathy, supplements, etc.