Just for fun: Scale of Universe

Click here for an interactive scale of the universe tool. So much fun!

Just for fun: World's first cell race

In a tongue-in-cheek contest of microscopic mobility, a line of bone marrow stem cells from Singapore beat out dozens of competitors to claim the title of the world’s fastest crawling cells. They whizzed across a petri dish at the breakneck speed of 5.2 microns per minute — or 0.000000312 kilometers per hour.

Western diet linked to increased intestinal disease

Picture from CIENCIASMEDICASNEWS

Westerners have been shown to be more susceptible to allergies, autoimmune disorders, and inflammatory bowel disease than residents of agrarian societies (one that is based on agriculture as its prime means for support and sustenance). A recent study suggests that people living in rural Africa have a healthier mix of microbes in their gut compared to their Western counterparts, which may protect them from the intestinal diseases that are common in modern developed countries.

The human gut is home to trillions of microbes (our microbiota) that help us digest and metabolize what we eat, protect us against diseases, and train our immune system to recognize and reject pathogens. As our diets change, so do our gut inhabitants -- from microbes that could easily break down fibrous foods that were plentiful in early human diets, to other bugs that can break down animal proteins, sugars, and starches that are prevalent in diets of Western civilization today. In addition, modern sanitation and medicines have further changed the types of bacteria that people encounter. Recent studies have suggested that people in developed countries are more susceptible to gastrointestinal diseases and obesity due to the different types of bacteria found in their digestive systems.

Read more about this research here.

Blood Cells and Immune Cells

(© Eric Reits, with changes by Claire Boog and Wilma Witkamp)

All blood cells are derived from the bone marrow. They are all the progeny of the common pluripotent haematopoietic stem cell. The haematopoietic stem cell then differentiates into a myeloid progenitor and lymphoid progenitor. The myeloid progenitor then further differentiates into blood cells, mast cells and monocytes. There are three types of blood cells: 

• Erythrocytes: commonly known as red blood cells. They carry nutrients and oxygen around the body to provide for other cells. 
• Leukocytes: commonly known as white blood cells. They are the main defenders of the body as is part of the immune system.
• Thrombocytes: commonly known as platelets. They form clots in sites of trauma to prevent blood loss while the body repairs the tissue.

Leukocytes are white blood cells and are highly important in immune response. There are many types of white blood cells each with their own function.

Neutrophil: they are very common and important in the innate immune response. Neutrophils are categorized as a granulocyte and are characterized by their multi-lobed nucleus that is observed when stained. They are the first cells to arrive at sites of inflammation and start phagocytosing foreign pathogens. They use the granules to degrade foreign material engulfed. Neutrophils are known to have myeloperoxidase as part of their granules.

Eosinophil: they are not so common leukocytes and are involved in parasite defence and allergic response. They are characterized by their bi-lobed nucleus when stained.

Basophil: they are important in allergic inflammatory responses and in the release of histamine.

Mast cell: mast cells are implicated in allergic inflammatory response as well as mast cell degranulation including the release of histamine and heparin. This usually results in severe allergic responses.

Monocyte: monocytes are blood cells that circulate in the blood stream till they move into a tissue and differentiate further into two more important immune cells: 

• Dendritic Cells (DC): these cells are easily characterized due to their arm-like dendrites extended from the cell. They tend to hang around in tissues and also the lymphatics. DCs are important antigen presenters as part of the adaptive immune system. They are characterized by the marker CD11c. 
• Macrophages: are also resident in tissues. Their main task is to phagocytose foreign pathogens and anything else that is not host.

The haematopoietic stem cell also differentiates into the lymphoid lineage and this leads to the production of lymphocytes. These cells are primarily located in the lymphatic system. The lymphoid progenitor leads to the production of two main types of lymphoid cells:

           

B-lymphocyte: acquire their name from the bursa of Fabricius in birds. They are matured in the bone marrow. They are important cells in the humoral immune system and the primary producers of antibodies. B-cells are initially called mature naïve cells, which means they are fully functional, but not yet ready or activated. They work together with other lymphocytes to be activated and start producing antibodies. B-cells are the third type of professional APCs. B-cells are also important for long term adaptive immunity.

T-lymphocyte: are also derived from the bone marrow. However, T-Cells travel to the thymus where they mature into CD4+ or CD8+ cells. The CD4+ T-cells usually become helper T-cells, which often work with B-cells in the adaptive immune system. The CD8+ T-cells are essentially killer cells that look for signals to kill other cells.

Dueling papers on bone growth and serotonin

Two groups of researchers have come to different conclusions on how serotonin levels affect bone density and production.(Article from NYTimes)

Click to read here

Common Terms

There is a plethora of terms and short forms in immunity. Therefore we will cover the most common ones.

Antibody (Ab): also known as immunoglobulin (Ig). These are protein structures that come in a general “Y” shaped form that often couple together to form other types of immunoglobulins. (i.e. IgA, IgD, IgG, IgE and IgM)

Antigen: a short term for antibody generator. This means that it can be any object that leads to an immune response or the generation of antibodies by the immune system.

Antigen presenting cells (APCs): are cells that present antigen to other immune cells that can then incorporate the antigen in its recognition. The most common antigen presenting cells are: dendritic cells, macrophages and B-cells.

Bursa of Fabricius: where the well known B-lymphocytes are originated from. I will go into more detail about these cells in the future.

Cluster of Differentiation (CD): these are important cell surface proteins that act as ligands, receptors, stimulatory molecules and have many other functions. They are important in the signalling of the immune system.

Complement: an innate response that is composed of three different types of responses. The complement system recognizes common and conserved markers on pathogens that home in other cells to eliminate them.

-cyte: this is the Greek term for a cell. It is almost always accompanied by a prefix that descries the type of cell.

Cytokines: this word is Greek for “cell” and “movement”. They are actually proteins whose function is to take part in cell signalling. Often a cell releases cytokines that go and bind to other cells that initiates a type of response.

Granulocytes: cells that contain granules that are often used to degrade intercellular material.

Inflammation: the swelling of tissue. An inflammatory response occurs when the immune system recognizes pathogens and a variety of cells and cytokines cause the local blood vessels to enlarge as well as swell up the local tissue.

Interleukin (IL-): interleukins are an important class of cytokines that have many cell signalling functions. They are always accompanied by a number suffix. (i.e. IL-1β, IL-13)

Ligand: anything that binds to a certain receptor. Ligands may be molecules or proteins. Often proteins and CD’s have –L suffixes to indicate if it is a ligand.

Major Histocompatibility Complex (MHC): there are two types of MHC: I and II. This is present on almost all cells (red blood cells do not) and allows the immune system to recognize self versus foreign.  Antigens are also presented by antigen presenting cells on MHC.

Phagocytosis: when a cell engulfs another cell or extracellular material. Often called cell-eating.

Receptor: any protein that acts as a receptor to a specific ligand. They often initiate responses once its ligand is bound. Often proteins, cytokines and CDs have –R suffixes to indicate if it is a receptor.

T-lymphocytes: commonly known as T-cells. These cells originate from the bone marrow and then mature in the thymus. They are important cells in the immune system and I will describe their functions more in the future.

Basic Immunology: Part 1

In the next series of posts we will cover an overview of immunology and the immune system, as well as a brief overview of common terminology. One thing everyone should understand is that the immune system is neither simple nor straightforward. It has many layers and types of defences as well as many pathways that are intertwined and interconnected. It can be quite confusing at first so bear with us.

Levels of Immunity

The immune system is divided up into multiple layers. This has evolved over millennia to provide us the necessary levels of defence against foreign pathogens. When a foreign object enters the body, it encounters the innate immune system, which is the first line of defence against foreign pathogens. This is a rather ubiquitous system and highly conserved among almost all living things on earth. Then comes the adaptive immune system, which is tends to act much slower. However, once it is activated it remembers that specific foreign object for life and upon future infection it acts almost immediately.

Picture from Centers for Disease Control and Prevention