Researchers analyzed human colon samples in a new study to map the interactions between gut bacteria populations and the immune system.
Human bodies are composed of a diverse array of cells forming various tissue types and providing an essential line of defense against possible disease-causing factors such as viruses and “evil” bacteria.
The human body’s main defense mechanism is the immune system, which enlists various types of highly specialized immune cells to keep the body systems “safe” and in good shape, defending them against harmful microbes.
And yet our bodies are also abundant in colonies of bacteria. We may be hosting as many as 38 trillion bacteria at any given time according to some researchers. Such bacteria most often help to maintain our state of health.
In the human body one of the most bacteria-rich areas is the intestine. Recent research has shown that gut bacteria can play a highly complex role within controlling various processes throughout the human body, with specialists even referring to a gut-brain axis.
Why, though, has a “machinery” as responsive as the human immune system allowed below micro-organisms to settle inside our guts? And how do immune cells deal with the bacteria in the gut?
These are some of the questions that the Wellcome Sanger Institute researchers in Hinxton, UK, recently aimed to tackle.
‘The microbiome is critical for health’
“The colon, as a barrier tissue, reflects a special immune environment in which immune cells display tolerance towards a diverse microbial population known collectively as the microbiome.” Senior author Sarah Teichmann, Ph.D., and her colleagues write in their new study paper featured in the journal Nature Immunology.
“The microbiome is important for many health aspects, and a commensal imbalance and pathogenic[ illness-causing] microbes are related to many disease states,” the authors of the study continue to write.
It is important to gain as detailed an understanding as possible of the interactions between gut bacteria and the immune system for these purposes, they demonstrate.
The current study is part of the project Human Cell Atlas, which seeks to provide a detailed reference map of all the cells within the human body.
“[ The report] provides a new understanding of the relationship between immune cells and microbiomas in healthy colon tissue and, by allowing us to specialize in cells in specific areas, it will be a crucial guide for ongoing work on diseases affecting specific colon regions,” says the senior author of the study.
As part of this project, the current research concentrated on mapping the interactions between gut bacteria and immune cells by analyzing postmortem samples from organ donors of healthy human colonists.
The researchers looked at the bacterial communities present in each segment and the immune cells that shared this community using samples from different segments of the human colon.
‘First in-depth map’
The team ended up analysing more than 41,000 immune cells ‘ regulated genes. This allowed them to recognize the genes that were triggered in the various types of immune cells present in each of the segments of the colon.
In addition, the investigators were able to find out which unique bacterial species in each of these parts of the human colon were present, offering new insights into how bacteria and immune cells communicate in the gut.
He observed that the various parts of the colon had different populations of resistant T cells.
Therefore, whereas in the colon’s cecum area— where the large intestine starts— T-helper 17 cells were most abundant, the sigmoid colon— the portion of the large intestine nearest to the rectum— had T-helper 1 cells in abundance.
This result supports prior observations from studies in mice, the researchers note.
The variations in the distribution of immune cells in the colon often balance differences in the distribution of bacterial populations.
One such example is that of the more abundant Bacteroides bacteria in the sigmoid colon, in the vicinity of the T-helper 1 cells.
The researchers demonstrate that current animal studies have shown that by releasing amounts of polysaccharides, certain bacteroids may be directly responsible for the proliferation of that particular set of T-helper cells.
“Our unique approach allowed us to create the first in-depth map of immune cells and their neighboring bacteria in the healthy human colon and revealed that, surprisingly, there are distinct immune niches across the colon, with different cell activation states in different areas.”– First author Kylie James, Ph.D.
Why the body ‘puts up with’ gut bacteria
But what are those results actually showing? The immune cells they found in the colon are regulatory immune cells, whose function is to decrease the strength of the immune response, according to the study authors.
The new research confirms previous mice work by indicating that these regulatory immune T cells initially migrated to the colon from lymph nodes— which play a key role in directing the immune response.
This step, and the very existence of regulatory immune cells in the colon, the investigators claim, may explain why bacteria can live in the gut without automatic rejection by the immune system.
“We are made up of as many bacteria as human cells and there is a symbiotic relationship between humans and their microbiota,” says co-author of the study Trevor Lawley, Ph.D.
“By exposing the complexity of the microbiome in different colon locations and the interactions with immune cells, we will begin to understand the biology behind this and inform future site-specific gut bacteria research.
Descending colon: What you need to know
The descending colon is a part of the large intestine. The colon’s left side is the one that descends. It is in charge of keeping the leftovers of digested food until they are eliminated through the rest of the colon and rectum.
The large intestine is involved in nutrient absorption. It also prepares the body’s waste products for removal.
The colon is the section of the large intestine that is the longest. Water and salt are absorbed, and liquid waste is solidified into stool. The ascending, transverse, descending, and sigmoid colons are the four primary parts.
We’ll look at the structure of the descending colon, as well as its function and the disorders that can affect it, in this article.
What is it?
The colon is the largest and longest part of the large intestine, and it is divided into four sections:
- the sigmoid colon
- the ascending colon
- the descending colon
- the transverse colon
The big intestine is a component of the gastrointestinal tract that connects to the small intestine on one end and the anus on the other.
The descending colon connects the transverse colon to the sigmoid colon and is the third primary portion. It begins from the splenic flexure, or bend, and finishes at the sigmoid colon’s junction. It’s called a retroperitoneal organ because it’s located behind the peritoneum. The peritoneum is the tissue that covers most of the abdominal organs and borders the abdominal wall.
The descending colon measures 10–15 cm in length. It’s in the abdomen’s left lumbar area. This area is located in the middle of the abdomen to the left. In this area, the descending colon runs in front of and down the left kidney.
The descending colon’s major function is to store hardened stool that will eventually empty into the rectum and be removed from the body.
The teniae coli, or smooth muscle bands, produce a series of pouches, or haustra, in all four sections of the colon. The colon appears segmented as a result of this.
The gastrocolic reflex is activated when the colon fills with digested food, causing peristalsis, which is a sequence of wave-like muscular contractions that assist move food along the digestive tract. Food can now pass from the descending colon to the rectum.
The colon’s overall function includes:
- forming and moving stool forward into the rectum for removal
- producing and absorbing vitamins
- absorbing water and electrolytes
The function of the descending colon and the colon as a whole may be affected by certain disorders. They may have an effect on the colon’s ability to absorb nutrients and create stool.
The following are some of the most prevalent descending colon health issues:
Another chronic inflammatory disease is Crohn’s disease. It’s an autoimmune condition that can affect any region of the digestive tract, including the colon, from the mouth to the anus.
Experts are unsure what causes Crohn’s disease, but they believe it is caused by an aberrant immunological response. Other factors, like as genetics and the environment, could also be at play.
Irritable bowel disease (IBD) includes both UC and Crohn’s disease.
A colonic or bowel perforation is a type of gastrointestinal perforation that occurs in the colon.
A cut, tear, or puncture in the colon’s wall can be caused by an injury, but it can also be caused by infection, obstruction, or inflammation.
A colonic perforation causes significant abdominal pain and often necessitates emergency surgery, which may include the removal of a portion of the intestines.
UC is an inflammatory condition that lasts for a long time. It is caused by immune system abnormalities that cause inflammation in the colon.
Ulcers form in the lining of the colon lining as a result of UC. This might cause in stool pain and the urge to stool regularly.
Experts are unsure of the actual cause of UC, however it could be caused by a condition of variables, including:
- environmental factors
- immune reactions
Cancer that begins in the colon or rectum is known as colorectal cancer. This happens when cancer cells in the colon start to grow out of control.
Colorectal cancers typically begin as polyps on the inner lining of the colon. However, not all polyps become cancerous, and the likelihood of a polyp becoming cancerous varies depending on the type of tumor present.
The size and location of tumors, whether the cancer is recurring, and a person’s overall health will all influence treatment. Among the possibilities are:
Diverticulitis is a condition in which small pouches or sacs called diverticula form and push outward through weak areas in the colon wall, causing inflammation.
These protrusions may not always be problematic, but when they get inflamed, they can cause symptoms like:
They can also cause problems including perforation and bleeding.
The following treatments may be used:
- using antibiotics
- in some cases, undergoing surgery
- increasing one’s dietary fiber intake
- taking pain relief medication
Tips for a healthy colon
People should eat a well-balanced diet, drink lots of water, and exercise regularly to maintain a healthy colon.
The American Cancer Society provides the following colon health recommendations to help minimize the risk of colorectal cancer:
- reducing consumption of red and processed meats
- reaching or maintaining a moderate body weight
- limiting or avoiding alcohol consumption
- having a diet that is rich in vegetables, fruit, and whole grains
- quitting smoking
- increasing dietary fiber intake
The big intestine includes the descending colon. It joins the transverse and sigmoid colon and is used to hold stool before it is emptied into the rectum.
The colon as a whole is responsible for absorbing nutrients from the diet as well as producing and releasing wastes.
IBD, colonic perforation, and diverticulitis are just a few of the health problems that can affect colon function.
Making healthy lifestyle choices, such as eating a balanced diet, exercising regularly, and limiting or avoiding processed meats and alcohol, can help to preserve intestinal health.
What to know about the rectum
The rectum connects the colon to the anus at the end of the large intestine. It’s the place where a person keeps their stool before excreting it.
The rectum, also known as the intestinum rectum, is a component of the digestive system that sits at the end of the large intestine. It is a connection between the GI tract and the anus. It sits after the sigmoid colon, the last portion of the colon, and is where the body stores excrement before expulsion.
The function and architecture of the rectum, as well as common disorders that may affect it, will be discussed in this article.
What is it?
The rectum is the last section of the large intestine closest to the anus, according to the National Cancer Institute. The large intestine is around 5 feet long in total, with the rectum accounting for about 12–15 centimeters of that length.
The intestines employ the muscular walls of the sigmoid colon to push excrement into the rectum when the digestive process is completed. The rectum is where the body stores excrement until it is time to defecate. When the rectum is full, stretch receptors in the wall sense it and stimulate the need to pass stool through the anus.
When to consult a doctor
If a person is having rectal discomfort or any other symptoms that could signal a problem around the anal area, they should see a doctor. Any rectal condition can have a negative impact on a person’s quality of life, so it’s preferable to address the issue as soon as possible to minimize problems. If a person is over the age of 50, they should talk to their doctor about having frequent rectal cancer screenings.
The large intestine is divided into four sections:
- Cecum: Also known as the ileocecal junction, this section joins the small and large intestines. The cecum helps absorb water and any remaining salts during the digestion process.
- Colon: The colon is the longest portion of the large intestine. It also absorbs water and electrolytes.
- Rectum: The rectum stores feces until a person is ready to have a bowel movement.
- Anal canal: The anus is the final portion of the large intestine. It helps a person have bowel movements.
Between the sigmoid part of the colon and the anal canal is where the rectum is located. The sacral and anorectal flexures are two primary flexures, or bends, in the rectum. There are also three lateral flexures, referred to as the Houston valves. These bends help sustain the weight of excrement while also preventing a strong and sudden urge to defecate.
The rectal ampulla, which connects the rectum to the anal canal, is located at the end of the rectum. The ampulla’s function is to act as a brief holding area for feces before it is released through the anal canal. When the ampulla fills up, the intrarectal pressure forces the walls of the anal canal to swell and expand, allowing excrement to enter.
Common rectal conditions
The following are some of the conditions that might affect the rectum:
Hemorrhoids are enlarged veins in the rectum and anus that protrude. They don’t always create symptoms, but when they do, patients may have the following symptoms:
- discomfort, irritation, or itching in the anal area
- pain in the anal area
- sensitive lumps
- bleeding during defecation
- protrusion of skin during bowel movements
A variety of infections can affect the rectum, causing itching, discomfort, and proctitis, among other unpleasant symptoms.
An individual may contract a sexually transmitted infection (STI) after indulging in anal sex, for example. This can include things like:
Antibiotics can sometimes cause a bacterial infection of the rectum. This is due to the fact that antibiotics can kill the good bacteria that keep pathogens like Clostridioides difficile , away. The germs can then grow out of control and invade the rectum.
Infections of the rectum and rectal tissues can also be caused by the fungus. The following are some examples of fungal diseases:
Parasites can enter the body and cause disease, especially when cleanliness is poor. Protozoa, which are single-celled organisms, and helminths, which are worms, are the two most common parasitic infections in the bowel. Parasites can cause a variety of issues affecting various parts of the gut, including the rectum.
A collection of pus in the tissue surrounding the anus or rectum is known as an anal abscess. One usually happens after an illness or an obstruction. A perirectal abscess is a type of rectal abscess that affects roughly 68,000–96,000 persons in the United States each year, according to data. A doctor would usually cut and drain the pus-filled cavity as part of the treatment.
Rectal prolapse occurs when a portion or all of the rectal wall passes through the anal sphincter, the seal that keeps the rectal contents contained. The weakening of the muscles that support the rectum is the most common cause of this illness.
Rectal prolapse can be classified into three categories:
- External: The entire rectum wall protrudes out of the anus, also known as full-thickness or complete prolapse.
- Mucosal: Only the mucosa, or anus lining, protrudes through the anus.
- Internal: Also known as an incomplete prolapse, the rectum folds in on itself but does not protrude out through the anus.
The rectum is vital for managing defecation and maintaining continence because it retains excrement. If a person’s rectum suffers from muscle injury, nerve damage, prolapse, or scarring, it’s possible that the rectum is unable to function properly, causing stool to seep from the anus.
Rectal cancer is a disease in which cancer cells grow in the rectum’s tissues. Rectal cancer can cause the following symptoms, which are not always present:
- bright red blood in stool
- leaks of diarrhea
- changes in bowel habits
Colon and rectal cancers are the second leading cause of cancer death in the United States. Surgery, radiation therapy, chemotherapy, targeted therapy, and immunotherapy are all possible treatment options.
Rectal health advice
People can try to practice proper anal hygiene to assist preserve rectal health and prevent rectal disorders. This can involve things like having regular bowel movements and using safer sex. Furthermore, lifestyle adjustments can aid in improving rectal health and lowering the risk of rectal cancer. These can include the following:
- avoiding alcohol
- reaching or maintaining a moderate body weight
- maintaining a nutritious, balanced diet
- avoiding smoking
- exercising regularly
The rectum connects the colon to the anus and is the last segment of the large intestine. It’s the place in the body where stool is kept until a person is ready to poop.
The rectal area can be affected by a variety of disorders. By producing pain, discomfort, and incontinence, any of these can lower quality of life. If a person is having problems with their bowels, they should see a doctor for a diagnosis.
Is there a link between IBD and microplastics?
In a recent small-scale investigation, researchers discovered a link between inflammatory bowel disease (IBD) and higher levels of microplastics in feces. The results were published in the journal Environmental Science & Technology.
The study, however, does not prove that microplastics cause IBD. More research is needed to confirm the findings and then seek an explanation for the link.
IBD is a broad term that refers to a variety of gastrointestinal disorders marked by inflammation. Crohn’s disease and ulcerative colitis are the two most frequent kinds.
Diarrhea, rectal bleeding, weight loss, abdominal pain, and exhaustion are all symptoms of IBD.
Researchers aren’t sure what causes IBD, but they believe it starts when a person who is genetically predisposed to the disease is exposed to a specific trigger. More research is needed to determine how important environmental triggers are.
IBD and microplastics
The researchers wanted to discover if there was a link between microplastics and IBD in this new study. Microplastics are present in people’s bodies throughout their lives, yet the health repercussions are unknown.
“We urgently need to know more about the health consequences of microplastics since they are everywhere—including in our drinking water,” says Dr. Maria Neira, WHO director of Public Health, Environment, and Social Determinants of Health.
“Microplastics in drinking water do not appear to constitute a health danger at current levels, based on the limited knowledge we have.” However, we need to learn more. We must also halt the global surge of plastic pollution.”
The current study’s corresponding author is Dr. Yan Zhang. He works at Nanjing University’s School of Environment’s State Key Laboratory of Pollution Control and Resource Reuse, where he previously discovered that microplastics accumulate in the liver, kidney, and intestine in animal models.
He also discovered that the particle size of the microplastics had a significant impact on the accumulation.
“Compelling evidence suggests that microplastics primarily collect in the guts of many species and induce intestinal inflammation and metabolic disturbance,” the researcher told Medical News Today. “Microplastics will inevitably come into contact with humans.”
“Estimating the exposure levels and loads of microplastics in people is crucial for assessing the health risk of microplastics.” However, accurate evidence on the effects of microplastics on humans is still unavailable. Furthermore, the actual health danger of human exposure to microplastics has long been a source of worry.
Because microplastics are routinely ingested through the gut, the researchers wanted to see if there was a link between microplastics and IBD.
They did this by examining fecal samples from study participants. The researchers gathered 52 persons with IBD and 50 people who were otherwise healthy but did not have IBD.
The participants answered questions on the foods and beverages they consume, their working and living conditions over the past year, the state of their IBD, and their demographic characteristics on a questionnaire.
The scientists then looked at the feces samples to see how much and what kind of microplastics were present.
Microplastics linked to IBD
They discovered that those with IBD had considerably more microplastic in their stools than those who were healthy.
Further research revealed a link between the severity of ulcerative colitis and Crohn’s disease and the number of microplastics present.
The researchers also discovered that persons who had more microplastic in their stool samples drank more bottled water, ate more takeout food, and were exposed to more dust where they lived or worked.
“For the first time, this study reveals that there is a significant difference in the concentration of microplastics in feces from IBD patients and healthy people. Our study also indicates that the characteristics of fecal microplastics are useful to estimate the gut exposure of microplastics.”
– Dr. Yan Zhang
“It’s difficult to say whether microplastics play a role in the development of IBD because it’s a complex systemic disease with an unknown etiology.” People with IBD are more likely to retain microplastics, we suspect.”
The study had flaws as well, the most significant of which was its small size. Before scientists can reach more solid findings, they must perform much larger investigations.
“The concentration of [microplastics] in feces found in this study cannot directly match the concentration of [microplastics] in the gastrointestinal system or in the human body,” the study authors write.
To put it another way, just though people with IBD excrete more microplastic doesn’t mean they have more microplastic in their bodies.