Your Immune system

Let's talk about the basic, front line defenders first. 

Macrophages are "Big eaters." It is a very correct and great name, since they do rip  enemies into little pieces by stretching out themselves, and catching enemies like bacterium and closed viruses with their "hands," which look more like tentacles. After that, the little parts of the ripped apart bacteria gets thrown into little pools of acid inside the Macrophage, much like our stomachs. And that is the end of the bacteria that decided to invade your body. This may sound gruesome and un-humane, but a much more helpless and violent death can happen...

...For there is a cell called the Neutrophil. They can explode into "NETS" of protein and acid, entrapping bacteria for Macrophages to devour. Or, another choice is to simply explode with much greater force and kill the bacteria. But, as you see here, we only say "bacteria." The main problem with Neutrophils are that those nets can damage civilian cells, like when police come to your house to find the thief and shoot you through the head because the thief was behind you.

There is an entire system called the complement system, in the bloodstream, harmless protein machines... harmless on their own... or until they are activated. Then after they are activated, they disable the bacteria, drill into them, and make little handles for macrophages. They are an entire army, just waiting to be activated. After they are, it will not be a very good day for intruders in your body.

Dendritic cells are messengers of the body. They collect antigens, small, useful pieces of the enemy and give it to T cells and B cells. They will self-destruct in about a week if they cannot find the right T cell.

Helper T cells are captains of your body's forces- they command and motivate macrophages to fight. They receive information on 'who is the enemy?' from the dendritic cell. They will also go to get the killer T cells.

Killer T cells, after being awakened by the helper T cells and Dendritic cells, will go to the battlefield and start searching for the antigen, destroying any cell that shows the antigen. (In the case of bacteria or viruses entering the cell.) They look through the MHC class 1 molecules, little windows that show up in a cell. They look for the wrong antigens, signs that the cell is being invaded.

B cells live in the bone marrow, and are the cells that make antibodies. After being informed by dendritic cells and helper T cells, they will produce antibodies that cover the antigen, rendering that important piece of the enemy useless.

Plasma B cells are made from activated B cells, when T cells give them a confirmation, and can provide lots of antibodies.

Natural killer cells are cells that look through the MHC class 1 molecules, but unlike killer T cells, who look for the known, they look for the missing- the loss of MHC class 1 molecules- for an invaded cell can be commanded by the attacker not to make those. 

ANTIBODIES:

IgM antibodies are the majority of antibodies that B Cells produce, and they are basically five antibodies together. They are useful with making the innate immune system more powerful.

IgG antibodies are specialists that are like complement but specialized towards the specific intruder.

IgA antibodies are found in lots of parts in the body, and clean up stuff in the mucosa, in the intestines, and sexual organs. They are like the guards at the front.

IgE antibodies are not much useful, but sometimes, they are crucial. They are the things that create allergies.