Lymphatic System

It depends somewhat on the cause and severity of the immune system compromise. In some situations, the recommendation is to wait for a week after the vaccination before being in close contact with some people who are immunocompromised. The Centers for Disease Control and Prevention information on the use of the intranasal live attenuated (weakened) vaccines includes the following excerpts:

In clinical studies, transmission of vaccine viruses to close contacts occurred only rarely. The current estimated risk of getting infected with vaccine virus after close contact with a person vaccinated with the nasal-spray flu vaccine is low (0.6%-2.4%). Because the viruses are weakened, infection is unlikely to result in influenza illness symptoms since the vaccine viruses have not been shown change into typical or naturally occurring influenza viruses.

People who are in contact with others with severely weakened immune systems when they are being cared for in a protective environment (for example, people with hematopoietic stem cell transplants), should not get the nasal spray vaccine, including the 2009 H1N1 nasal spray vaccine if they will come into contact with the severely immunocompromised person within 7 days of vaccination. People who have contact with others with lesser degrees of immunosuppression (for example, people with diabetes, people with asthma taking corticosteroids, or people infected with HIV) can get the nasal spray vaccine. The full information at the CDC website about vaccines is available at the link provided in the related links section below.

There are 2 parts to the immune system, general (also called innate) and specific (also called adaptive). The general immune system is made out of immune cells that attack anything deemed bad by the general immune system, and don't specify later. The specific immune system is made of cells that specialize in targeting specific germs and other bad things [viruses, bacteria, fungi, small animals (yes, small animals can infect you, such as worms), damaged/ dying/ malfunctioning cells etc.].

When a germ first comes in (swine flu in this case), the general immune system responds. The skin is actually the first line of defense, but apparently it got past that. Mast cells are land mines. When tripped they "blow" releasing histamines, which tell the surrounding tissues to inflame, and draw other parts of the immune system to the scene. The inflammation tries to tighten the area up, to make it harder for what was detected to get in.

Neutrophils are one of the first types of cells responding to the inflammation, and come to try and kill off bacterial infections with anti-microbial secretions. If things get intense, dead neutrophils pile up and form pus.

Monocytes, half of which are stored in the spleen, come to the area changing into macrophages and dendrites. There is a muddled line between these 2 forms of the cell. Macrophages gobble up germs and other foreign junk they find, and shred the junk into pieces inside it. The pieces are then carried to the surface of the cell, where they are put on antigen-presenting proteins (platters of display, if you will). Think of it as a hunter holding the head of his prize buck. Displaying of antigens (the shreds of the invader) is what dendrites do (muddled line).

Transitioning to the specific immune system, the cell then carries its "catch" to a helper T-Cell that changes its shape to match the shape of the antigen, but in the negative form of the shape (negative, as in cast and mold negative, as in one fits in the other like a peg in a hole). When its shape fits into the antigen shape, that helper T-Cell releases chemokines that draw killer T-cells and plasma cells to the site of infection.

Once activated, a plasma cell is called a B-Cell. B-cells shoot antibodies, which are like arrows coming from an archer. The antibodies bind to the germs, disable them, and mark them for destruction by the immune system.

Killer T-Cells are VERY special. So far in these steps, the immune system has been only able to recognize things by what's on their surface. Killer T-Cells actually connect to a cell, look beneath the surface to find out if it is infected with the virus, and kill the cell if it is, before the thousands of replicated viruses manufactured in that cell can get loose. Everything in the cell gets broken down, so the viruses made in there thus far don't make it out "alive" to infect new cells.

When the infection has been killed off, T-regulatory cells put out the "stop-fighting signal", and immune memory gets stored. "Immune memory", refers to the process of the killer and helper T-cells and B-cells, that where involved in the fight, keeping the pattern of the germ for future reference. Then they go hibernate in a lymph node somewhere. If the same or very similar germ reappears some day, these memory immune cells are able to immediately react and kill the infection almost instantly (because they already know the shape of the antibody that is needed for that specific invader).

Don't forget to recycle! After the infection is over, all the dead cells get broken down to make new cells. Material from germs that has been properly broken down is safe to make cells out of as well, which the body does.