Your concern is very interesting but common and wide. As you know that Ayurvedic system of medicine is more or less rely on the medicinal plants products or herbal formulation that enhance/boost the immune system in order to treat/manage/heal/cure the particular disease.

To be in short, herbal/plant formulations boost our immunity either by preventing the down regulation of immune system or by enhancing/activating immune system of our body. As you know due to over increasing population that results in the limited resources and large competition generates stress.

The stress is now deeply rooted in the society and almost every one is having some or other kind of anxiety & stress (factors including unemployment, lack of opportunities, limited resources, large competition and from last two years the COVID-19 pandemic). Several herbal/plant products/formulations reduce the stress and thereby preventing stress-mediated down regulation of immune system. As you know the stress whether it is physiological (due to oxidative stress, pharmacological (due to drugs), and psychological (due to mental stress) can induce immune cells (cell mediated immune system of our body) death either by apoptosis, necrosis, necroptosis, autophagy etc pathways and thereby immunity. Reduction of stress ( physiological/ pharmacological/psychological) by herbal/plant products/formulations are easily managed by Clinicians in Ayurvedic system of medicine. You can find out the list of medicinal plants that are used to prepare harbal formulations and ayurvedic medicines.

The second important mechanism by which the herbal/plant products/formulations increase immunity is through boosting/increasing both enzymatic (Catalase, SOD, Glutathione perxidase, Lipid perxdase etc.) as well as nonenzymatic (such as Vitamins, carotene, flavanoids) antioxidants in our body. As you know that these antioxidants directly or indirectly scavenge free radicals and oxidants, reduce oxidative stress, prevent cellular damage caused due to stress and most importantly rejuvenate the immune system as well.

As you know that the large number of herbal medicines are reported to prevent tumor formation, anti-cancer activities and enhance immune system by reducing stress generated in cancer patients.

Aloe vera, St. John's wort, and licorice have been shown to boost immunity. Garlic is another plant that boosts the immune system. It contains allicin, ajoene, and thiosulfinates that help prevent and fight infection. The Neem, Tulsi, Ashwagandha, Triphala, Ginger, Garlic, Turmeric etc are also used to boost our immunity.

This ancient medical science had stated long ago that plant extracts could do a lot to strengthen the body. According to Ayurveda, our body can withstand infections only when all the seven layers of our body’s tissues (Rasa, Mamsa, Rakta, Medha, Majja, Asthi and Shukra) are strong. When the seven layers are working together, our immunity will be boosted.

I suggest you to go through several peer reviewed international journals that publishes research papers on herbal medicines that induce immunity. Many research papers are available that describe the possible mechanism of herbal medicine action at the cellular and molecular level in order to boost up immunity of our body.

Hope this may be useful

Best

Plant extracts are actually chemical compounds and the same applies to other medicinal chemical compounds in terms of stimulating, inhibiting and various other effects on the cells and systems of the body.

http://njppp.com/fulltext/28-1487571016.pdf

Article Immunity: Plants as Effective Mediators

https://downloads.hindawi.com/journals/jir/2018/9172096.pdf

Hello Anil Kumar Thakur

Phytochemicals present in plants are reported to be primarily responsible for immunomodulatory effects acting as immunomodulators. They are known to modulate the immune system in non-specific ways. They can stimulate or suppress the innate or adaptive immunity. They are classified in terms of their molecular weights, as high molecular weight consisting of peptides and polysaccharides and low molecular weight compounds like terpenes, alkaloids and phenolics.

The main course of action of these compounds is to influence non-specific immune response mainly by enhancing phagocytosis and proliferation of macrophages and neutrophils. Based on structure and functional groups, these plant derived compounds will bring about different effects on immune cells. For instance, the chain length of flavanol fractions has a significant effect on cytokine release from both unstimulated and LPS-stimulated PBMCs. But in the absence of stimulation, both the long chain- and short chain- fractions can stimulate the production of GM-CSF and increased expression of B-cell markers CD69 and CD83.

Also, several plant phenolic compounds can influence dendritic cell function, especially in a suppressive way. Because Th1 cells are either functionally immunogenic or provide protection against invading pathogen, the inhibition of DC-mediated Th1 polarization may constitute an associated immunosuppressive mechanism.

The bioavailability of plant derived compounds is another issue. Low absorption and rapid elimination can cause limited bioavailability.

Please refer to the article attached for more information.

Chapter Plant Phenolic Compounds as Immunomodulatory Agents

Best.

As per your concern, the genesis of diseases by interfering the immune system is not a new phenomenon. In terms of bishransa (displacement), vyapada(improper functioning) & kshaya(deficiency) of Ojas (immune strength), It has been learly concieved in centuries old system of medicine I.e. Ayurveda. Its management has been also described by adopting different measures in which Plants are are important source for diets and drugs. Recent experimental & Clinical evidences regarding Guduchi, haridra, Pippali, tulasi, amalaki, madhuyashthi, ashwagandha, kalamegha etc not only justified the classical indications where they were mentioned but also justfied that above plants boost immunity by interfering the immune mechanism of the body. So, we can say that since ancient times Ayurveda boost the immune system through it's own way by incorporating the diet, lifestyle & drugs. It is believed that the only sustainable way to survive in the current situation is to boost the immune system but it is not true. It is the right time for scientific community to come forward to explore the hidden secrets of Ayurveda (diet, lifestyle and plants) on molecular basis for the benefit of society in general & disease in particular.

Thank you, Prof. Shail K Chaube Sir.

I am specifically interested in knowing which specific group of phytochemicals is involved in boosting the immune system. Whether they modulate the innate or adaptive or both immune systems. Which specific group of immune cells is up-regulated/down-regulated through the immune response?

Regards

Thank you for very informative answer, Dr. Malcolm Nobre ji

Regards

Thank you for informative links, Ali Ahmed Azzawri

Regards

Thank you for your very informative reply, Dr. Ajai Kr Pandey Ji

I am specifically interested in knowing which specific group of phytochemicals is involved in boosting the immune system. Whether they modulate the innate or adaptive or both immune systems. Which specific group of immune cells is up-regulated/down-regulated through the immune response?

Regards

Many phytochemicals are antioxidants which have been shown to enhance the immune system, especialloy in the elderly. Here's a recent abstract: https://www.sciencedirect.com/science/article/abs/pii/S0891584922000016

Plant-derived xenomiRs may also be beneficial.

Thank you for introducing me to the beneficial role of exogenous miRNAs (xenomiRs) in health/immune modulation, Dr. Don Kaiser Ji.

Regards

Thank you, All