Laughter is VERY Sexy to Your Immune Cells

/Laughter is VERY Sexy to Your Immune Cells

Laughter is VERY Sexy to Your Immune Cells

Laughter is an
Immune Cell

AND laughter’s a key factor in sexual selection for women

Have you noticed the more you laugh with a date the more “friendly” you become?  Personally, the second love-of-my-life kept me in stitches!

So it was something of an “ahah” moment after reading studies published by Jeffery Hall in Evolutionary Psychology  that challenge the notion women prefer men who are funny because we view it as a sign of intelligence. In a series of three experiments, Professor Hall demonstrated that men who deliver the best punchlines score much higher on the attraction scale regardless of their IQ. Interestingly, the reverse wasn’t true —  that is, men DON’T find humor in women  particularly sexy (1a). (For fun, check out Hall’s Flirting Styles Inventory to “use the science of flirting to attract the love you really want.”) Hah — there’s even a “science of flirting!”

Could it be that women live longer BECAUSE laughter makes us want to mate???  As women, we’re hardwired to favor partners who deliver the best punchline versus the most cerebral pick-up line. Aside from the aerobic benefits of a good bedroom workout, recent advances in psychoneuroimmunolgy (PNI) – the science of laughter as medicine — show us that humor builds immune cells. show.  The stronger our immune systems, the longer we live!

Laughter makes carpal tunnel surgery recovery go faster too!

Brain Brief


One of the best feelings in the world is a heartfelt, knee-slapping belly laugh!

Read on to find out how laughing as much and as often as you can is literally a life-saver.

Meet your body’s most potent immune cell: the Natural Killer Cell

photo courtesy NIH

Natural Killer Cell is such a cool term you’d think I made it up. The honor belongs to Eva Klein who coined it in 1975 to describe her discovery of an immune cell with the very special property of being born a killer(1). Other immune cells have to jump through scores of communication hoops and metamorphoses before they can do their work of annihilating invaders. Most importantly, Natural killer cells (NKs) are unique in that they can destroy diseased HUMAN cells. In simple-speak, NKs kill tumors on contact and they roam the lymph system and bloodstream looking for offenders making them a focal point of cancer therapy research.

For sure, the more NKs a gal has on her side — the better! Are you laughing yet?

Eva and George Klein

Eva Klein is extraordinarily cool herself. Born Eva Fischer in 1925, she was working as an actress attending medical school at the University of Budapest in Hungary when WWII broke out. She met and fell in love with a fellow student named George just eight days before he left for Sweden as part of a Jewish student group. George found a haven in Stockholm in the Cell Research Department of the Karolinska Institute. He returned to Budapest and the couple secretly married before narrowly escaping the death camp transports using false papers. The couple worked together at the Institute until George’s death in 2016. Eva published more than 500 journal articles in the field of tumor biology. Her most recent publication at the age of 92 appears in the April 2017 issue of Oncogene.

Researchers continue to uncover remarkable features about NKs considered an “evolutionary bridge” between our innate and adaptive immune systems. The innate system is our front line defense against illness while the adaptive system kicks in when the going gets really tough. Think of the adaptive system as the body’s special forces while the innate system is more like a beat cop’s daily patrol.

Natural Killers (NK) in the Innate System

As beat cops, NKs do spectacular work vigilantly patrolling the body seeking out foreign invaders and cancer cells. They kill by drilling holes in the target cell membrane allowing water to rush in causing them to swell and burst.

It bears repeating they’re the only immune cells that can destroy diseased human cells. It’s almost a touching story how cells sacrifice themselves for the sake of the health of the whole. Every nucleated cell in the body carries on its surface a protein named MHC1. When a healthy cell becomes overwhelmed by a virus, it changes the structure of MHC1 to become MHC2 sending out a chemical messenger asking to be destroyed.

NK cells go around the body arbitrarily testing cells for MHC2 and when they find one, they go to work. Just one NK cell can live for as long as two months navigating the body via blood and lymph seeking out and destroying threats(2a).

NK Cells in the Adaptive System

They Keep Files!

This aspect of NK activity is a relatively new finding.

The adaptive immune system describes the activity of cells that copy the genetic code of invaders and keeps records on them so the body is prepared should they show up again. This is the basis of how vaccinations work. A dead virus is injected into the blood stream and special Memory Cells copy their genetic code so the body can manufacture custom antibodies.

The exciting news is that NK cells, once thought to exclusively belong to the innate system, have evolved to also keep files on foreign invaders.

This is really important because NK cells act fast. Other immune warriors have to be told to kill a pathogen in a signalling process that happens relatively slowly. Because NK cells come to the party with loaded guns, their importance to maintaining health  in light of the ever growing list of dangers is growing. They can do their work BEFORE an infection or cancer takes hold.



How Natural Killer Cells do their job

Wow! Laughter boosts Natural Killer Cell activity by 40 percent

Does Bill Cosby, Tim Allen or Robin Williams make you laugh out loud? If so, you may have just almost doubled the number of NKs roaming your body ready to pounce on pathogens.

Dr. Mary Bennet of Indiana State University picked up on previous research investigating laughter’s effects on immune cell activity. She choose to measure blood levels of NKs because earlier studies using saliva assays of immunoglobin A (IgA) to determine effect are of questionable clinical significance. She selected women as participants because previous studies used men.

Dr. Bennet’s team divided 33 women with normally functioning immune systems into a control group and a humorous video group. The control group watched a boring travel video while the humor group selected from Bill Cosby, Himself; Tim Allen, Men are Pigs; or Robin Williams, Live at the Met. Self-reported stress and arousal levels, mirthful laughter, and NK levels were measured.

Results: Self-reported stress was reduced in both groups suggesting that boredom is calming. However, those who laughed out loud scored highest on stress relief and showed the highest increase in NK levels — up to 40 percent(2)! Are you laughing yet?

Laughter makes carpal tunnel surgery recovery go faster too!

Laughter is especially healthy for diabetes patients

Takashi Hayashi is a researcher working at the Foundation for Advancement of International Science in Tsukuba, Ibaraki, Japan. He’s published a series of studies showing a good belly laugh is particularly restorative for the 360 million people worldwide living with type 2 diabetes (3).

In one straight-forward study, recruited 19 type 2 patients  for a two-day experiment. On both days, their fasting blood glucose was measured before eating the same 500kcal lunch. On day one following the meal, participants watched a monotonous University lecture for 40 minutes. On the second day after the meal,  they watched a comedy show for the same length and laughed a lot! Glucous levels were measured again two hours after the meal. The average blood sugar levels on day two dropped by 37 percent(4)!

Dr. Hayashi conducted a similar version of the above study but reversed the order of the days. They watched the funny show on day one and the boring lecture on day two.  His team confirmed the drop in postprandial blood glucose but this time also ran assays on 18,716 genes. They found that on the day participants watched the funny video that their bodies up-regulated eight genes and 15 were down-regulated. However none of these genes are involved in glucose metabolism leaving the question of HOW laughter lowers blood sugar still unanswered(5).

Digging further, Hayahi’s team repeated the study but this time recruited patients admitted to the hospital for self-management education. On day one, they watched a funny video laughing with hospital staff and on day two attended an inpatient diabetes education program.

The team expanded the number of genes they investigated to 41,000 and found that laughter up-regulated 39 genes. Fourteen of those genes are involved in natural killer cell activity! But they still couldn’t find any difference in genes that control blood sugar (6).

Finally, the team ran a shortened version of the experiment to look for changes in receptor genes for prorenin. This is important for type 1 diabetes patients because when blood levels of prorenin rise above normal all kinds of vascular problems arise including retinopathy that can lead to blindness and neuropathy that can lead to foot amputations(7).

This time, both diabetes patients and normal subjects watched a funny video. In the diabetes patients, laughter significantly decreased blood levels of prorenin but no changes were found in the normal subjects(8).  Are you laughing yet?

Just Relaxing Gets Immune Cells Multiplying

Although it make take as long as a week!

The beauty of laughter is that there are immediate peaks in immune cell activity. This experiment focused on the effects of relaxation, stretching and breathing exercises.

Researchers enrolled study participants in a week-long yoga program featuring meditation, postures and breathing practices. The control group took nature walks and listened to relaxing music.

Participants had their blood measured for “peripheral blood mononuclear cells” (PBMCs) before and after the program. PBMC is a way to describe cells that have one nucleus, most of which category are immune cells.

Specifically, the researchers were looking for changes in the gene expression of T cells, B cells and natural killer cells.

Before and after every yoga practice, participants stuck out their arms to have 20 ml of blood withdrawn. Yikes!

The results? Compared with controls, the yoga group expressed three times more changes in circulating immune cell genes(9).

Satisfying the Last of the Doubting Thomas’s

Crossover studies are designed to prove or disprove assumed links between cause and effect factors.

In our case, we’re assuming that smiling produces a rise in natural killer cell activity. BUT is it the emotion behind smiling or the physical act of lifting the corner’s of one’s mouth that accounts for the immune system benefits? Interesting question.

The Japanese geniuses behind the diabetes type 2 and NK activity cited above designed a crossover experiment to test the assumption that smiling does indeed cause a positive effect. Ready for this?

They attached electrodes to participants’ smile muscles and then shot electric currents through the electrodes to force the corners of their mouths up!

They varied the amount of electricity to vary the magnitude of the smile. Each time they varied the intensity of the electricity — they drew blood to look for natural killer cell activity.

The results? The bigger the smile the more natural killer cell activity(10).


(1a) 1) Hall JA. Sexual Selection and Humor in Courtship A Case for Warmth and Extroversion. Evolutionary Psychology. 2015.

(1) Sun, Joseph C., and Lewis L. Lanier. “Natural Killer Cells Remember: An Evolutionary Bridge between Innate and Adaptive Immunity?” European journal of immunology 39.8 (2009): 2059. PMC. Web. 6 June 2017.

(2) Bennet, Mary, JM Zeller, and L. Rosenberg. “The Effect of Mirthful Laughter on Stress and Natural Killer Cell Activity.” Altern Ther Health Med. 9.2 (2003): 38-45. Web.

(3) Santos-Longhurst, Adrienne. “Type 2 Diabetes Statistics and Facts.” Healthline. Healthline Media, 27 Feb. 2017. Web. 07 June 2017.

(4) Hayashi, K., T. Hayashi, and S. Iwanaga. “Laughter Lowered the Increase in Postprandial Blood Glucose.” Diabetes Care 26.5 (2003): 1651-652. Web.

(5) Hayashi, Takashi, Osamu Urayama, and Koichi Kawai. “Laughter Regulates Gene Expression in Patients with Type 2 Diabetes.” Psychotherapy and Psychosomatics75.1 (2006): 62-65. Web.

(6) Hayashi, Takashi, Satoru Tsujii, and Tadao Iburi. “Laughter Up-regulates the Genes Related to NK Cell Activity in Diabetes.” Biomedical Research 28.6 (2007): 281-85. Web.

(7) “Complications.” Diabetes Forecast. American Diabetes Association, Oct. 2013. Web. 07 June 2017.

(8) Hayashi, Takashi, Osamu Urayama, and Miyo Hori. “Laughter Modulates Prorenin Receptor Gene Expression in Patients with Type 2 Diabetes.” Journal of Psychosomatic Research 62.6 (2007): 703-06. Web.

(9) Rapid Gene Expression Changes in Peripheral Blood Lymphocytes upon Practice of a Comprehensive Yoga Program

(10) The elevation of natural killer cell activity induced by laughter in a crossover designed study

Eva Klein
Reflections on Denmark and Hungary During WWII
Eva Klein Group Karolinksa Institute

Natural killer cells remember: An evolutionary bridge between innate and adaptive immunity?

Eva Klein Group

Natural Killer Cells: Innate or Adaptive Immunity? Or Both?

Immune System Overview

The Immune Response Animation

Natural Killer Cell Memory

By | 2019-03-09T00:59:43+00:00 August 29th, 2017|Laughter as Medicine, Lifestyle Science|0 Comments

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