"Ashwagandha was accompanied by significant increases in hemolytic antibody responses towards human erythrocytes."
https://pubmed.ncbi.nlm.nih.gov/8866726/
"Effects on immune cell activation with use of Ashwagandha warrant further study." https://pubmed.ncbi.nlm.nih.gov/19388865/
"Commonly combined with other herbs, astragalus has been promoted as a dietary supplement for many conditions, including upper respiratory infections, allergic rhinitis (hay fever), asthma, chronic fatigue syndrome, and chronic kidney disease, among others. It’s also promoted to strengthen and regulate the immune system."
https://www.nccih.nih.gov/health/astragalus
"The major components of Astragalus membranaceus are polysaccharides, flavonoids, and saponins. Contemporary use of Astragalus membranaceus mainly focuses on its immunomodulating, anti-oxidant, and anti-inflammatory, as well as anticancer effects."
https://pubmed.ncbi.nlm.nih.gov/26916911/
"Echinacea is promoted as a dietary supplement for the common cold and other infections, based on the idea that it might stimulate the immune system to more effectively fight infection."
https://www.nccih.nih.gov/health/echinacea
"Traditional herbal medicine provides several remedies for strengthening the body's resistance to illness through effects on immune system components. This review article examines 3 popular herbal immune stimulants that are often of interest to cancer patients. Echinacea, a native of North America, is widely used to prevent, or provide early treatment for, colds. Preclinical studies lend biological plausibility to the idea that echinacea works through immune mechanisms. Numerous clinical trials have been carried out on echinacea preparations: it appears that the extracts shorten the duration and severity of colds and other upper respiratory infections (URIs) when given as soon as symptoms become evident."
https://pubmed.ncbi.nlm.nih.gov/15035888/
"Elderberry may be a safe option for treating viral respiratory illness, and there is no evidence that it overstimulates the immune system. However, the evidence on both benefits and harms is uncertain and information from recent and ongoing studies is necessary to make firm conclusions."
https://pubmed.ncbi.nlm.nih.gov/33827515/
"Angie Kuhn, MS, RDN, and nutritionist with Persona Nutrition, says that elderberry, thanks to its high antioxidant content, can help improve the immune system."
https://www.popsugar.com/fitness/what-does-elderberry-do-for-immune-system-47090289