CD11b Expression and the Innate Immune System

Why CD11b is important in Immunity: (Ref: Novus Biologicals)

CD11b is an integrin - Integrins are receptors that mediate attachment between a cell and the tissues surrounding it.
CD11b is expressed on the surface of many leukocytes including monocytes, neutrophils, natural killer cells, granulocytes and macrophages, as well as on 8% of spleen cells and 44% of bone marrow cells.
Functionally, CD11b regulates leukocyte adhesion and migration to mediate the inflammatory response.
CD11b antibody studies have shown the protein to be directly involved in cellular adhesion, although migration can only take place in the presence of the CD18 subunit.
As well as playing a role in various adhesion reactions, CD11b is a receptor for complement C3bi, mediating complement-coated particle uptake. Research using CD11b antibodies has identified CD11b as a receptor for fibrinogen gamma chain peptides, factor X and ICAM1, with possible roles in cell-mediated cytotoxicity, chemotaxis and phagocytosis.
Until recently, mouse CD11b expression had only been reported in detail for neutrophils and monocytes. In 2005, Kawai et al. undertook a CD11b antibody study to clarify CD11b function in B cells. Flow cytometry was used to isolate peripheral CD19+ B cells, and their migratory function was verified via transwell assays. Using CD11b antibody preparations, the contribution of Cd11b to migratory ability was then determined. It was seen that naïve B cells had little migratory capability and were CD11b negative. Memory B cells, however, had a high degree of motility and expressed CD11b. Given these findings, the authors suggested that CD11b plays an essential role in memory cell migration.

Nk Cells - Natural Killers

See Science Daily for their definition and explanation of Nk Cells.

Key points:

• NK cells play a major role in the elimination of both tumours and virally infected cells.
• NK cells are cytotoxic; small granules in their cytoplasm contain special proteins such as perforin and proteases known as granzymes.  Granzymes are enzymes that break down proteins and are released by natural killer cells. Their purpose is to induce cell-death within virus-infected cells, thus destroying them.
• Upon release in close proximity to a cell slated for killing, perforin forms pores in the cell membrane of the target cell through which the granzymes and associated molecules can enter, inducing cell-death (apoptosis).
• The distinction between apoptosis and cell lysis is important in immunology - lysing a virus-infected cell would only release the virions, whereas apoptosis leads to destruction of the virus inside. NK cells are activated in response to interferons or macrophage-derived cytokines.

Check the video out on NK cells

A small fraction (~2%) of the lymphocytes circulating in the blood are neither T cells nor B cells.  Most of these are called natural killer (NK) cells because they are already specialized to kill certain types of target cells, especially

• host cells that have become infected with virus;

• host cells that have become cancerous.

Advice to writers of blogs, articles and books

From WORLD WIDE WORDS (Issue 763 Sat 19 Nov).
Let your conversation possess a clarified conciseness, 
   compacted comprehensibleness, coalescent consistency, and 
   a concatenated cogency. Eschew all conglomerations of 
   flatulent garrulity, jejune babblement, and asinine 
   affectations. Let your extemporaneous descantings and 
   unpremeditated expatiations have intelligibility, without 
   rhodomontade or thrasonical bombast. Sedulously avoid all 
   polysyllabical profundity, pompous prolixity, and 
   ventriloquial vapidity. Shun double-entendre and prurient 
   jocosity, whether obscure or apparent. In other words, 
   speak truthfully, naturally, clearly, purely, but do not 
   use large words.
   [Notes and Queries, 11 Feb. 1893.]

Sugar, Fat & Insulin

Insulin (from HowStuffWorks)

When you eat a meal, the presence of sugars, amino acids or fatty acids in the intestine stimulates the pancreas to secrete a hormone called insulin. 

Insulin tells the cells to do the following:

• Absorb glucose, fatty acids and amino acids.
• Stop breaking down glucose, fatty acids and amino acids; glycogen into glucose; fats into fatty acids and glycerol; and proteins into amino acids.
• Start building glycogen from glucose; fats (triglycerides) from glycerol and fatty acids; and proteins from amino acids.

The activity of lipoprotein lipases depends upon the levels of insulin in the body. If insulin is high, then the lipases are highly active; if insulin is low, the lipases are inactive.  This means that Fat will potentially build up!

The fatty acids are then absorbed from the blood into fat cells, muscle cells and liver cells. In these cells, under stimulation by insulin, fatty acids are made into fat molecules and stored as fat droplets.

Fat cells can absorb glucose and amino acids from the bloodstream after a meal, and convert those into fat molecules. 

The conversion of carbohydrates or protein into fat is 10 times less efficient than simply storing fat in a fat cell, but the body can do it. If you have  just 100 extra calories in fat (about 11 grams) floating in your bloodstream, fat cells can store it using only 2.5 calories of energy. On the other hand, if you have 100 extra calories in glucose (about 25 grams) floating in your bloodstream, it takes 23 calories of energy to convert the glucose into fat and then store it. Given a choice, a fat cell will grab the fat and store it rather than the carbohydrates because fat is so much easier to store.