Figure 5.

Host factors associated with resistance to immunotherapy in cancer patients. (I) Gender is a factor due to the physiological differences between the innate and adaptive immune systems. (II) Age is indicated in studies as the elderly are more likely to develop resistance than their younger counterparts. (III) Malnutrition may interfere with cell-mediated immune responses, which may allow individuals to develop resistance to immunotherapy. (IV) Pregnancy-associated physiological adjustments, including immunotolerance, could interfere with immune recognition and, subsequently, lead to resistance. (V) Microbiomes, such as Bifidobacterium, A. muciniphila, Faecalibacterium, and Bacteroidales, were associated with the enhancement of the immune response in cancer patients, while imbalances in the microbiota were abundant in cancer patients developing resistance to immunotherapy. (VI) Obesity was shown to increase resistance to immunotherapy using animal models of cancer. (VII) Stress is an environmental factor associated with the modulation of immune responses that weaken adaptive immune responses, leading to the failure of the response to immunotherapy. (VIII) Hormones, such as testosterone, estrogen, and progesterone, also modulate the innate and adaptive immune responses, leading to variable responses to immunotherapy in both genders. Created with BioRender.com.