The ABC’s of the Human Immune System

The ABC's of the Human Immune System

Immunity is your body’s natural protection system, and it carries out two primary functions—defense and tolerance. Your immune system defends against external invaders—think bacteria, viruses, and parasites—and it patrols your body for internal troublemakers, such as cancer cells. It also regulates your level of tolerance to potential environmental triggers, such as allergens (including pollen, bee stings, grasses, wheat, peanuts, soy, and corn).

When your immune system performs these two functions optimally, it helps keep you healthy. However, when your defenses don’t do their job, or your body’s tolerance level is too low or becomes overwhelmed, it makes you more vulnerable to infections, cancer, and autoimmune disorders, as well as increasing your risk for depression, anxiety, and even psychosis.

Your immune system performs its important mission in 4 ways:

  • Identifies external invaders or internal cells or tissues that are misbehaving
  • Recruits your white blood cells to attack the bad guys
  • Tags and decimates external and internal problems
  • Remembers invaders and troublemakers in case they return

The 4 Primary Immune System Functions

  • against the external environment: If it fails, you get an infection.
  • against the internal environment: If it fails, you get cancer.
  • against the external environment: If it fails, you get allergies.
  • against the internal environment: If it fails, you get an autoimmune disease.

Immune disorders fall into one of 5 categories, all of which impact your brain health/mental health:

1. Immunodeficiency disorders:

These disorders can either be present from birth or result from an illness, such as human immunodeficiency virus (HIV) or acquired autoimmune deficiency syndrome (AIDS), which damages your immune system. People with HIV are twice as likely to experience depression, and they also have an increased risk of anxiety and cognitive disorders, including dementia.

2. Allergies:

When your immune system views neutral environmental “visitors,” such as pollen or pet dander, as enemies, it can lead to allergies, asthma, eczema, or even life-threatening consequences. In a 2018 study including over 186,000 people, those with asthma, hay fever, and eczema were 66% more likely to develop psychiatric disorders compared with those without allergies. And asthma has been shown to increase the risk of dementia by 30%.

3. Cancers of the immune system:

Leukemia and lymphomas are the most common forms of cancer affecting the immune system. Cancer of any kind has long been associated with detrimental changes in emotional health, and research shows that cancer patients are more likely to have a mental health issue than people without the disease. In fact, as many as 25% of cancer patients have clinical depression.

4. Autoimmune disorders:

When your immune system mistakes your own internal tissues for troublemakers and attacks them, it can create an autoimmune disorder. I typically refer to this as “friendly fire.”

5. Persistent infections:

When you experience recurring infections, it may be an indicator of a compromised immune system.

Excerpted from “The End of Mental Illness” by Daniel G. Amen, MD.

At Amen Clinics, our psychiatrists and Integrative and Functional Medicine physicians treat a wide range of conditions and make recommendations for pro-active therapies to enhance or restore the immune system. For more information, speak to a specialist today at 888-288-9834. If all our specialists are busy helping others, you can also schedule a time to talk.


  1. Not very helpful as I had hoped to learn how to make my immune system stronger…..especially with Corona here. Does fasting work to make the system aware of a virus and to fend it off? I understand that some victims of the 1918 Spanish flu were not fed as they were expected to die and they recovered. How about some useful information or don’t you know?

    Comment by scott w francis — April 3, 2020 @ 3:07 AM

  2. How can you increase immune system.? Took immunotherapy for 8 years, helped a bite. Have UC, and now Parkinson’s.

    Comment by Linda ehemann — April 3, 2020 @ 3:17 AM

  3. Thank you. I’m glad I read this. I need to do more QiGong.
    I need to clear my mind of negative thoughts.

    How do I help my 97 year old father survive in personal care with no visitation for 22 days. It’s like solitary confinement and we know what that does to a mind and body.

    Comment by Linda Ziegler — April 3, 2020 @ 4:11 AM

  4. Dr. Amen: I have had Hashimoto’s thyroiditis since age 35 but not treated until age 37 because it was erratic. The endocrinologist who did all my testing put me on 150 mcg of Synthroid at that time. Then my husband and I moved from CA to MO 30 years ago, in 2015 they started cutting back on my Synthroid and put me levothyroxine up and down since then and I am on finally at 100 mcg of Synthroid again. I am 76 now and and don’t understand why I feel so labored and low energy just since the low-level of care I have received since moving after my husband’s death and moving here to Doniphan, MO. There is no quality of care here and I am still active and care for myself and the home I rent, also only go for blood tests every 4 months plus checkup with my doctor. Plus, I have emphysema from my husband smoking all the years we were married. I had an appointment to see my doctor and a counselor for checkups but the Carona-19 virus has me on hold. Took care of myself all my life but running too much from age 10 years old until to age 37 now have right knee replacement and they want to do another. I’m struggling with internal softening of my bones and right falling arch. I don’t smoke and don’t drink but feel over-looked because I am old, but feel the same internally as I did at 63. Always paid attention to my vitamins and minerals since the age of 17, is took regular mammograms since age of 30. Also spent years diving and swimming. road my bicycles and exercised— now they say my bones are softening. Shocked by my lifelong practice of healthy living but now I’m old and and within the past year feel ill ?? I pray but ask why?? I have in one year gone down this path.

    I’ve been on calcium + 3000 D3 q.d. since around age 45. Now they have me on prescription calcium and D3. My dentist remarked about my bone strength until I got an infection in my right side upper jaw where he put the implants and repaired that with bone cement. Help please!! l need someone with expertise to help me now. I still feel viable even with some dementia. Thank you for taking your time to read this. Sincerely, Ruth Dodd

    Comment by Ruth M. Dodd — April 3, 2020 @ 6:43 AM

  5. Hello Scott, thank you for reaching out. We are hosting a webinar on this topic as well, if you’re able to tune in April 8th:

    Comment by Amen Clinics — April 3, 2020 @ 7:43 AM

  6. Hello Linda, thank you for reaching out. We are hosting a webinar on this topic as well, if you’re able to tune in April 8th:

    Comment by Amen Clinics — April 3, 2020 @ 7:44 AM

  7. My concern is how prescription drugs, 5 or more, affect our immune system.

    Comment by Alexandra Dewispelaere — April 3, 2020 @ 11:18 AM

  8. Qigong & tai Chi are excellent for immune system. There are many of both on You Tube.
    Some specifically for Immune system.

    Comment by Beverly Maher — April 4, 2020 @ 4:35 AM

  9. I wish you had a clinic in the Chapel Hill, Raleigh, Durham area. I would love to take advantage of your knowledge but your clinics are to far away. Any chance of opening one in this area.?

    Comment by Barbara Renton — April 4, 2020 @ 7:38 AM

  10. At what time on April 8th?

    Comment by Barbara — April 4, 2020 @ 11:31 AM

  11. Dr Amen. I wonder what do you think about chronic stress?
    How High level of cortisol does affect on our immune system?
    Please advise.

    Comment by Ilan Perry — April 4, 2020 @ 7:17 PM

  12. If started using OZONE daily you would achieve a lot just there..

    I’m surprised how little in Amen mention about OZONE that apparently is magic………literally,

    Youtube..’Medical Ozone Therapy’ and read……….it is the first thing you should use before Far Infrared…..which is cool. And home hyperbarics which I did for 2 years………and was going to do again until

    David Brownstein and the American Academy of Ozone Therapists…….found me……

    I now have had my home OZONE generating equipment……….for two weeks and have no knee pain for the first time in 20 years, without meds, and still ruined knees the my Orthopedist said need a full replacement…Allopathy is a pagan religious cult that Amen et al are finally taking down. But definitely need to researh and get on the Ozone wagon…….. before any food change or supplement or herb or hormone……..Ozone forever……..then add stuff…Wm R.Kelso, II, M.D.

    Comment by William Robert Kelso — April 4, 2020 @ 7:29 PM

  13. Sorry to hear that Mrs. Dodd. But as someone who had “regular mammograms since age of 30” it is hardly a surprise you have some serious problems.

    If people had the correct information about the dangers of x-rays they’d stop having them.

    The real truth is that it had been known to medical science for decades that low dose (even the lowest possible dose) x-rays are very dangerous (eg they interfere with thyroid function, hamper energy metabolism, cause cancer, especially breast cancer — read the books “Preventing Breast Cancer: The Story Of A Major, Proven, Preventable Cause Of This Disease” by John Gofman and “The Mammogram Myth” by Rolf Hefti), but the corrupt business of organized medicine has been disregarding, denying, downplaying, and obfuscating these scientific fact ever since.

    Comment by Terry — April 4, 2020 @ 8:10 PM

  14. Some of what you shared reminds me of what my sister-in-law has gone through. She’s exasperated with our current unhealthy foods and medical system, and has found a lot of help using an iodine protocol. Apparently we need iodine for every system to be well and toxins in our food and environment hinder its function.
    May you find good answers in your quest; I hope you’ll share what you learn and more of us be benefited too.

    Comment by Ruth — April 5, 2020 @ 10:35 AM

  15. We really enjoyed the webinar. Would it be possible to get a copy of the slides in the presentation?

    Comment by John & LoRae/Amen clinic patients, Orange County, CA location — April 8, 2020 @ 12:09 PM

  16. We are glad that you enjoyed the webinar! Here is a link for you to view/share:

    Comment by Amen Clinics — April 8, 2020 @ 2:50 PM

  17. How can avoid getting dementia. On april 17th , I will reach my 80th birthday and dementia runs in my family. Please email me the prevention for that terrible decease. Thanks.

    Comment by Elena valentin — April 9, 2020 @ 4:51 AM

  18. My question is: I have Diabetes 2, but my numbers are low. A1c is 6.2 Here is my problem. I have varicose veins for years and had vein surgery many times. My upper legs are just fine, but the veins are in my feet, and the color is blue & painful red marks. I also have numbness, tingling, pain like being stabbed. Is this entirely from my diabetes problems or is it the veins?

    Comment by Reba Dick — April 16, 2020 @ 9:42 AM

  19. Do you have any treatment insight for autoimmune hepatitis?

    Comment by T — November 1, 2023 @ 9:02 AM

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