Dendritic Cells Activating a Lymphocyte

Here is a beautiful scanning electron micrograph of a human lymphocyte (pink) as it scans the surface of a dendritic cell (blue).

Lymphocytes are white blood cells, of which there are three types: B cells, T cells, and natural killer (NK) cells. Dendritic cells are located in the tissue and are responsible for stimulating the adaptive immune response via the activation of T cells.

As someone who has studied minimal immunology yet works in a research group comprised of ~80% immunologists, I’m always ready for a refresher.  And here is that refresher, based on the seasonal allergies that come with the Spring season.

ucsdhealthsciences:

What’s up your nose 
           
Spring is in the air, and for folks with allergies, that means pollen too, signaling a season of sneezing, snuffling and sniveling. Seasonal allergies are an annoying sign that your body’s immune system is doing its job, which is basically to provide protection against environmental toxins that may be far more dangerous than pollen.
           
The immune response is roughly divided into two types: innate and adaptive.
           
Innate (or type 1) refers to a nonspecific form of immunity, a natural-born resistance to various pathogens, from viruses and bacteria to fungi and protozoa. It involves both barriers to keep pathogens out and internal methods for directly killing invaders or infected cells.
           
Adaptive (or type 2) immunity is specific, a learned response resulting from previous exposure to a toxin. It can be naturally acquired or artificially, as in vaccines.
           
In type 2 immunity, the body sends specialized T cells and antibodies to deal with a specific irritant. Sometimes, they go too far – at least for our immediate comfort.

In a paper published in the journal Nature recently, researchers at Yale University suggest that the nasty symptoms of seasonal allergies are the result of environmental allergens like pollen revving the body’s immune system into overdrive.

The result: Over-production of  the neurotransmitter histamine and its consequent coughing, sneezing, runny noses and general suffering. 
           
As much as we might hate them, though, seasonal allergies may be a sign of evolved status. “We believe that allergic hypersensitivity evolved to survey the environment for the presence of noxious substances,” said lead author Ruslan Medzhitov, a professor of immunobiology at Yale. “After the first exposure, the immune system gains a memory, and subsequent exposure to even minute amounts will induce an anticipatory response that helps minimize potentially harmful effects.”
           
Keep Medzhitov’s words in mind next time you’re insanely congested from airborne allergens. They might help.

Or not.
          
Above: A scanning electron micrograph of various pollen from common plants: sunflower, morning glory, hollyhock, lily, primrose and castor bean. The pollen has been magnified 500 times.

(via realfakescientist)