July 8, 2010

Blood Basics

 The Components of Blood and Their Importance

Blood Basics

Blood is a specialized body fluid. It has four main components: plasma, red blood cells, white blood cells, and platelets. Blood has many different functions, including:
  • transporting oxygen and nutrients to the lungs and tissues
  • forming blood clots to prevent excess blood loss
  • carrying cells and antibodies that fight infection
  • bringing waste products to the kidneys and liver, which filter and clean the blood
  • regulating body temperature
The blood that runs through the veins, arteries, and capillaries is known as whole blood, a mixture of about 55 percent plasma and 45 percent blood cells. About 7 to 8 percent of your total body weight is blood. An average-sized man has about 12 pints of blood in his body, and an average-sized woman has about 9 pints.

The Components of Blood and Their Importance

Many people have undergone blood tests or donated blood, but hematology – the study of blood – encompasses much more than this. Doctors who specialize in hematology (hematologists) are leading the many advances being made in the treatment and prevention of blood diseases. If you or someone you care about is diagnosed with a blood disorder, your primary care physician may refer you to a hematologist for further testing and treatment.


The liquid component of blood is called plasma, a mixture of water, sugar, fat, protein, and salts. The main job of the plasma is to transport blood cells throughout your body along with nutrients, waste products, antibodies, clotting proteins, chemical messengers such as hormones, and proteins that help maintain the body's fluid balance.

Red Blood Cells (also called erythrocytes or RBCs)

Known for their bright red color, red cells are the most abundant cell in the blood, accounting for about 40-45 percent of its volume. The shape of a red blood cell is a biconcave disk with a flattened center – in other words, both faces of the disc have shallow bowl-like indentations (a red blood cell looks like a donut).

Production of red blood cells is controlled by erythropoietin, a hormone produced primarily by the kidneys. Red blood cells start as immature cells in the bone marrow and after approximately seven days of maturation are released into the bloodstream. Unlike many other cells, red blood cells have no nucleus and can easily change shape, helping them fit through the various blood vessels in your body. However, while the lack of a nucleus makes a red blood cell more flexible, it also limits the life of the cell as it travels through the smallest blood vessels, damaging the cell’s membranes and depleting its energy supplies. The red blood cell survives on average only 120 days.

Red cells contain a special protein called hemoglobin, which helps carry oxygen from the lungs to the rest of the body and then returns carbon dioxide from the body to the lungs so it can be exhaled. Blood appears red because of the large number of red blood cells, which get their color from the hemoglobin. The percentage of whole blood volume that is made up of red blood cells is called the hematocrit and is a common measure of red blood cell levels.

White Blood Cells (also called leukocytes)

White blood cells protect the body from infection. They are much fewer in number than red blood cells, accounting for about 1 percent of your blood.

The most common type of white blood cell is the neutrophil, which is the “immediate response” cell and accounts for 55 to 70 percent of the total white blood cell count. Each neutrophil lives less than a day, so your bone marrow must constantly make new neutrophils to maintain protection against infection. Transfusion of neutrophils is generally not effective since they do not remain in the body for very long.

The other major type of white blood cell is a lymphocyte. There are two main populations of these cells. T lymphocytes help regulate the function of other immune cells and directly attack various infected cells and tumors. B lymphocytes make antibodies, which are proteins that specifically target bacteria, viruses, and other foreign materials.

Platelets (also called thrombocytes)

Unlike red and white blood cells, platelets are not actually cells but rather small fragments of cells. Platelets help the blood clotting process (or coagulation) by gathering at the site of an injury, sticking to the lining of the injured blood vessel, and forming a platform on which blood coagulation can occur. This results in the formation of a fibrin clot, which covers the wound and prevents blood from leaking out. Fibrin also forms the initial scaffolding upon which new tissue forms, thus promoting healing.

A higher than normal number of platelets can cause unnecessary clotting, which can lead to strokes and heart attacks; however, thanks to advances made in antiplatelet therapies, there are treatments available to help prevent these potentially fatal events. Conversely, lower than normal counts can lead to extensive bleeding.

Complete Blood Count (CBC)

A complete blood count (CBC) test gives your doctor important information about the types and numbers of cells in your blood, especially the red blood cells and their percentage (hematocrit) or protein content (hemoglobin), white blood cells, and platelets. The results of a CBC may diagnose conditions like anemia, infection, and other disorders. The platelet count and plasma clotting tests (prothombin time, partial thromboplastin time, and thrombin time) may be used to evaluate bleeding and clotting disorders.

Your doctor may also perform a blood smear, which is a way of looking at your blood cells under the microscope. In a normal blood smear, red blood cells will appear as regular, round cells with a pale center. Variations in the size or shape of these cells may suggest a blood disorder.

Normal blood smear.
The four larger cells shown are called granulocytes, a type of white blood cell.

Abnormal blood smear with variation in the size and color of the red blood cells.

Where Do Blood Cells Come From?

Blood cells develop from hematopoietic stem cells and are formed in the bone marrow through the highly regulated process of hematopoiesis. Hematopoietic stem cells are capable of transforming into red blood cells, white blood cells, and platelets. These stem cells can be found circulating in the blood and bone marrow in people of all ages, as well as in the umbilical cords of newborn babies. Stem cells from all three sources may be used to treat a variety of diseases, including leukemia, lymphoma, bone marrow failure, and various immune disorders.

Where Can I Find More Information?

If after further exploration of the Blood: The Vital Connection Web site you find that you are interested in learning more about blood diseases and disorders, here are a few other resources that may be of some help:

Articles From Hematology, the ASH Education Program Book
The American Society of Hematology (ASH) Education Book, updated yearly by experts in the field, is a collection of articles about the current treatment options available to patients. The articles are categorized here by disease type. If you are interested in learning more about a particular blood disease, we encourage you to share and discuss these articles with your doctor.

Results of Clinical Studies Published in Blood
Search Blood, the official journal of ASH, for the results of the latest blood research. While recent articles generally require a subscriber login, patients interested in viewing an access-controlled article in Blood may obtain a copy by e-mailing a request to the Blood Publishing Office.

Other Resources
This section includes a list of Web links to patient groups and other organizations that provide information.


Thrombocytopenia and the risk of bleeding during treatment with peginterferon alfa and ribavirin for chronic hepatitis C

J Hepatol. 2010 Jun 1. [Epub ahead of print].

Roomer R, Hansen BE, Janssen HL, de Knegt RJ.

Department of Gastroenterology and Hepatology, Erasmus MC University Medical Center Rotterdam, Rotterdam, The Netherlands.


BACKGROUND & AIMS: Chronic HCV patients with baseline thrombocytopenia are often excluded from treatment with peginterferon alfa and ribavirin or undergo many dose reductions of peginterferon alfa. The aim of this study was to investigate the correlation between thrombocytopenia and the occurrence of bleedings during antiviral treatment for HCV infection. METHODS: In this single center cohort study 2876 visits of 321 patients treated with peginterferon alfa and ribavirin were evaluated for thrombocytopenia, bleedings and dose reductions during HCV treatment. RESULTS: Mean platelet count at baseline was 207,000/mul for non-cirrhotic patients (n=253) and 132,000/mul for cirrhotic patients (n=68). Mean platelet drop was 42% from 191,000 to 113,100/mul (range 8000-284,000/mul). Severe thrombocytopenia (platelet counts <50,000/mul) was observed in 30 patients (9.3%) at 166 visits and 9 patients developed platelet counts <25,000/mul at 15 visits. Forty-eight bleedings were observed in 27 patients (8.4%). Only one bleeding, due to gastrointestinal angiodysplasia, was defined as severe. However, this patient did not have severe thrombocytopenia at the time of bleeding. During visits, patients reported more minor bleedings when platelet counts were <50,000/mul compared to visits with platelet counts 50,000/mul (11.4% vs. 1.1%, p<0.001). In the multivariate analysis, platelet count of <50,000/mul was a significant predictor of bleeding (p<0.001). CONCLUSION: Severe bleedings did not occur in patients with platelet counts below 50,000/mul; based on these findings, treatment with peginterferon alfa and ribavirin appears to be safe in patients with platelet counts below 50,000/mul although platelet counts below 25,000/mul were rare. Copyright © 2010. Published by Elsevier B.V.

PMID: 20561709 [PubMed - as supplied by publisher]


Kenner Boy Dies Of Rare Bacterial Infection

John Lopez Contracted Bacteria While Walking On Beach

POSTED: 3:58 pm CDT July 8, 2010
UPDATED: 7:07 pm CDT July 8, 2010

KENNER, La. --

It was supposed to be a fun family trip to the coast to check out a car show, but it ended with the death of a 12-year-old Kenner boy.

John Lopez, lovingly called "John-John" by friends and family, unknowingly contracted a deadly bacteria after walking in the water.

"They were there for a car show and within 24 hours, he got ill with this parasite," said John's sister, Crissy Harvard.

John walked on the beach, and only his feet touched the water. A short time later, he became sick. Doctors said he was infected by a bacteria called Vibrio Vulnificus, which is rare. But for people like John, who had existing medical problems, the infection is deadly.

"When you have chronic disease like HIV, liver problems, you're predisposed, and infection could form and it could be fatal," said WDSU medical editor Dr. Corey Hebert.

Hebert said you can get this infection if you are in salt water with an exposed cut or scratch, or a pre-existing condition. John's family said he had a small sore on his foot, and suffered from Hepatitis C.

Doctors said if he had survived, he would have lost his arms and legs. But on Saturday, John-John passed away.

"This is horrible. It breaks my heart," said his mother, Wendy Harvard. "He's only 12. He just made 12."

Hebert said not everyone is at risk for this infection. Those with pre-existing conditions are most at risk, but he said everyone should pay attention to their bodies.

"When you walk through brackish water and get cut, don't ignore it," Hebert said. "Go to your doctor if it turns red or if you feel really bad."

The Vibrio Vulnificus bacteria can cause heart failure, loss of limbs or even death.
See Also: Vibrio Vulnificus

The recent breakthroughs in the understanding of host genomics in hepatitis C

European Journal of Clinical Investigation

Early View (Articles online in advance of print)

Published Online: 6 Jul 2010

Journal Compilation © 2010 Stichting European Society for Clinical Investigation Journal Foundation

Andri Rauch * , Janine Rohrbach * and Pierre-Yves Bochud †
* University Clinic of Infectious Diseases, University Hospital Bern and University of Bern, Bern , † Department of Medicine, Service of Infectious Diseases, Institute of Microbiology, University Hospital and University of Lausanne, Switzerland

Correspondence to Andri Rauch, MD, University Clinic of Infectious Diseases, Inselspital PKT2B, 3010 Bern – Switzerland. Tel.: +41 31 632 15 74; fax: +41 31 632 31 76; e-mail: andri.rauch@insel.ch

Copyright Journal Compilation © 2010 Stichting European Society for Clinical Investigation Journal Foundation

Hepatitis C treatment • hepatitis C virus • host genomics • interleukin 28B • spontaneous clearance
Eur J Clin Invest 2010


Background Hepatitis C Virus (HCV) infection is spontaneously resolved in about 30% of acutely infected individuals. In those who progress to chronic hepatitis C, HCV therapy permanently eradicates infection in about 40% of cases. It has long been suspected that host genetic factors are key determinants for the control of HCV infection.

Design We will review in this study four genome-wide association studies (GWAS) and two large candidate gene studies that assessed the role of host genetic variation for the natural and treatment-induced control of HCV infection.

Results The studies consistently identified genetic variation in interleukin 28B (IL28B) as the strongest predictor for the control of HCV infection. Importantly, single nucleotide polymorphisms (SNPs) in IL28B strongly predicted both spontaneous and treatment-induced HCV recovery. IL28B is located on chromosome 19 and encodes interferon-λ, a type III interferon with antiviral activity, which is mediated through the JAK-STAT pathway by inducing interferon-stimulated genes. The SNPs identified in the GWAS are in high linkage disequilibrium with coding or functional non-coding SNPs that might modulate function and/or expression of IL28B. The role of the different IL28B alleles on gene expression and cytokine function has not yet been established.

Conclusions These findings provide strong genetic evidence for the influence of interferon-λ for both the natural and treatment-induced control of HCV infection, and support the further investigation of interferon-λ for the treatment of chronic hepatitis C. Furthermore, genetic testing before HCV therapy could provide important information towards an individualized HCV treatment.

Received 9 April 2010; accepted 9 June 2010

10.1111/j.1365-2362.2010.02337.x About DOI


Hemochromatosis (Iron Storage Disease) Awareness

July is hemochromatosis (iron storage disease) awareness month. Hemochromatosis occurs when the body absorbs too much iron from foods (and other sources such as vitamins containing iron). If this iron buildup is untreated, it can, over many years, damage the body's organs. Learn the symptoms and how to stay healthy.

Hemochromatosis (Iron Storage Disease) Awareness

July is hemochromatosis (iron storage disease) awareness month. Hemochromatosis occurs when the body absorbs too much iron from foods (and other sources such as vitamins containing iron). If this iron buildup is untreated, it can, over many years, damage the body's organs. Learn the symptoms and how to stay healthy.

What is hemochromatosis?

Hemochromatosis occurs when the body absorbs too much iron from foods (and other sources such as vitamins containing iron). This disease causes extra iron to gradually build up in the body's tissues and organs, a term called iron overload. If this iron buildup is untreated, it can, over many years, damage the body's organs.

What are the causes?

Although hemochromatosis can have other causes, in the United States the disease is usually caused by a genetic disorder. A person who inherits the defective gene from both parents may develop hemochromatosis. The genetic defect of hemochromatosis is present at birth, but symptoms rarely appear before adulthood. Because one inherits genes from his or her parents, this type of the disease is also called hereditary hemochromatosis.

What are the symptoms?

Early indications of hemochromatosis include the following symptoms:
  • Fatigue (feeling very tired)
  • Weakness
  • Weight loss
  • Abdominal pain
  • Joint pain
Because these symptoms also occur with other diseases, hemochromatosis can be difficult to diagnose in its early stages.

How is it detected?

If your doctor suspects you have iron overload associated with hemochromatosis, there are two blood tests – serum transferrin saturation and ferritin levels – which may be used to help make the diagnosis. The tests measure how much iron is in the body. You can have these tests done in your doctor's office.

If hemochromatosis is detected early, treatment can slow its progress and prevent serious problems. However, if the disease is not detected and treated early, it can cause more serious problems. These problems include arthritis, heart problems, and liver problems (such as cirrhosis and liver cancer).

If you think you have symptoms like those of hemochromatosis or if you have a close blood relative who has hemochromatosis, you should ask your health care provider to check the amount of iron in your blood.

What is the treatment?

Treatment consists of periodically taking blood from the arm, much like giving blood. The treatment is safe and effective. Patients can expect a normal life span if they start treatment before organ damage has begun.

Most people with hemochromatosis should be checked at least once a year to be sure that their iron level is within the normal range. If the iron level is too high, phlebotomy treatments are needed to keep extra iron from building up in the body.

Tips for Living Well with Hemochromatosis

There is much you can do to make sure your life is as normal and healthy as possible.
  • Check-ups: Have the amount of iron in your blood checked regularly.
  • Phlebotomy: Make sure to get phlebotomies when you need them. Phlebotomy is the best treatment for hemochromatosis. Hemochromatosis cannot be treated by changing your diet alone.
  • Iron pills: Don't take iron pills, supplements, or multivitamin supplements that have iron in them. Eating foods that contain iron is fine.
  • Vitamin C: Vitamin C increases the amount of iron your body absorbs. Avoid taking pills with more than 500 mg of vitamin C per day. Eating foods with vitamin C (such as oranges) is fine.
  • Food: Don't eat raw fish or raw shellfish. Cooking destroys germs harmful to people with hemochromatosis. People with hemochromatosis are at greater risk for bacteremia, a bacterial infection of the blood stream.
  • Alcohol: If you choose to drink alcohol, drink very little. Women should have no more than one drink a day. Men should have no more than two drinks a day. However, if you have liver damage, do not drink any alcohol.
  • Exercise: You can exercise as much as you want. The CDC and the American College of Sports Medicine offers the following physical activity recommendations: Adults should engage in moderate-intensity physical activities (indicated by someincreasein breathingor heart rate) for at least 30 minutes on preferably all days of the week.
More Information

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Page last updated: July 5, 2010

Content source: National Center on Birth Defects and Developmental Disabilities, Division of Blood Disorders

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URL for this page: http://www.cdc.gov/Features/Hemochromatosis/