Leukocytes and Antibodies

Time to study physiology again! :)

Leukocyte (aka white blood cell) Types
Contents (scroll down or click to learn more about each)

1. Neutrophils*
2. Eosinophils*
3. Basophils*
4. Natural Killer cells
5. Monocytes
6. Lymphocytes
1. B cells
2. T cells

*First 3 are granulocytes, meaning they have little granules inside which get released as they are activated
1-4 are nonspecific immunity, the rest are specific

Neutrophils

• Most abundant white blood cells - about 55-75%
• Nonspecific immunity
• Phagocytotic - eat bacteria mostly
• They take in the bacterium into a vesicle which then fuses to a lysosome inside the cytoplasm and the digestive enzymes contained within the lysosome kill the bacterium
• Diapedesis (squeezing through blood vessel walls to get to the site of infection)
• Made in the bone marrow
• Live for hours in the blood, a couple days in the tissues
• Follow chemotactic factors given off by the resident mast cells near the site of infection (like a trail of bread crumbs!)

Oh my gosh! I just realized my favorite video is showing this process pictured in the above diagram!  You have to watch this, it's the greatest thing ever, but if you're wise you'll actually view it through this link to the creators' website because it's much better quality.  But just in case you need it, I also uploaded the version from YouTube.

And then there's this 8 minute version which has some things labeled for the true nerds.  And this confirms that this is in fact a neutrophil doing diapedisis at the end. :)  Geek out moment!

Eosinophils

• 2-4% of WBC's
• Phagocytotic -  antigen-antibody complexes
• Diapedesis
• Fight parasitic infections
• Phagocytose antigen-antibody complexes
• May detoxify foreign proteins 
• Granules release toxic substances such as free radicals that kill bacteria and parasites
• Made in the bone marrow
• Live in blood for a few hours, and a couple days in tissue

 Basophils

•  0.5-1% of WBC's
• Become resident Mast Cells in the tissues
• Inflammatory cell, does liquifaction
• Have granules in them filled with histamine (and stuff)

 Mast Cells (grown up Basophils)

• Mast cells become activated by being damaged or by activated compliment, or a protein from neutrophils.  Since they live in the tissues, it makes sense that they are there kind of as the alarm system- if you cut your finger, mast cells in that tissue will be activated, starting the ball rolling on immunity.
• When "degranulated" (activated), mast cells immediately release:

• histamine - increases local blood flow and capillary permeability in the infected area
• heparin - anti-clotting factor to help prevent clotting from getting out of control or spreading beyond where it needs to be
• chemotactic factor - attracts neutrophils and eosinophils to come to the area of infection and take care of business (or DTTTD as Shively would say..do that thing they do)
• platelet activating factor - does what the name implies
• More slowly (over a couple minutes), also releases:
• prostaglandins
• leukotrienes

• Play big role in allergies because of the histamine (to remember- you may have heard that "anti-histamines" are allergy meds).  Very severe allergies can lead to anaphylactic shock which is life threatening and can kill a person very quickly.  Since histamine dilates the capillaries, if it goes systemic, this would lead to lethally low blood pressure, which is why epinephrine must be immediately administered, which constricts blood vessels and gets blood pressure back up.  (Woohoo, I get that now!)

Natural Killer Cells

• Nonspecific immunity
• Work similarly to cytotoxic T cells
• Insert perforin into foreign cells - basically a big protein with a hole in it so the cell ends up with a gaping hole and everything leaks out, lysing the cell
•  

Monocytes

• Phagocytotic - can kill thousands of bacteria (see the cool picture)
• Diapedesis
• Become macrophages in the tissues
• Nonspecific immunity
• Live for a few hours in the blood, months or years in the tissue
• Memory cells

Macrophages - (grown up monocytes)
The name "macro" "phage" refers to phagocytosis - they are awesome phagocytosers (I'm sure that's not really a word, sorry.  But you get the idea.)

4 types:

• tissue macrophages - in all tissues of the body
• Kupffer cells - line sinusoids of liver
• Alveolar macrophages - line alveoli of lung
• Microglia - in the brain

Release stuff:

• Colony stimulating factors - sends the message to bone marrow to stimulate the production of more WBC's
• Cytokines - (interleukine-1, interleukine-6, tumor necrosis factor) - these do many things, but the one that stands out (to me) is activating T and B cells so specific immunity can be developed.

This is super cool.  This is a macrophage in a mouse reaching out its pseudopodia to grab and engulf antigens.  Macrophages don't sit around and wait for stuff to come to them!

B Lymphocytes

• Circulation pattern: lymph nodes - lymph - blood - tissue spaces - lymph
• Make antibodies
• Start their development in the bone marrow, then some of them travel to the liver to finish maturing
• Specific immunity
• humoral immunity (humor = body fluids), don't do hand-to-hand combat
• Once exposed to an antigen, they differentiate into memory cells or plasma cells

Memory Cells

• When an antigen is processed by a macrophage, it presents part of the antigen on its surface for the B-cell to be exposed to
• These memory cells then divide and conquer, literally.  They multiply into both more memory cells and plasma cells

Plasma Cells

• Antibody mass-producing factories
• Only live 3 days

T Lymphocytes

• Attack abnormal, foreign, or virus-infected cells
• Cell-mediated immunity (T cells have to be in contact with the cell they attack)
• Three types:
• Cytotoxic T cells
• Helper T cells- release cytokines that stimulate production of different cell types, inhibit migration of macrophages, and direct immune cells to site of infection.
• Suppressor T cells

Antibodies

Immunoglobulins
IgG - most abundant, produced when body is subsequently exposed to antigen
IgA - mucus membranes, all things opening to the surface - breast milk, tears, saliva, etc
IgE - activates mast cells to release histimine
IgM - serve as the B cell surface receptor and is secreted in early stages of plasma cell response
IgD - is found on surface of B-lymphocytes (antibodies)


Sources:
Much of this info is paraphrased from physiology course notes by Dr. Heather Ashworth at UVU
Supplemental info paraphrased from wikipedia and others such as:
http://www.biosite.se/viewpage.aspx?pageid=289
This site has a very detailed and awesome overview of all this stuff, so if you need more info, go here: http://www.pc.maricopa.edu/Biology/rcotter/BIO%20205/LessonBuilders/Chapter%2015%20LB/Ch15LessonBuilder_print.html