What is Cellular Immunity?

Mary McMahon
Mary McMahon

Cellular immunity, also known as cell-mediated immunity, is an important aspect of the immune system that allows the body to attack invading organisms on a cellular level. It is paired with humoral immunity, the part of the immune system that involves an antibody response. Both types of immunity are a critical part of a healthy and functioning immune system.

The immune system uses a series of interconnected systems to catch infectious organisms.
The immune system uses a series of interconnected systems to catch infectious organisms.

In cellular immunity, the body recognizes infected cells and kills them, using cells like macrophages and natural killer cells. These cells are designed to trigger cell death, ensuring that infected cells do not replicate and allow the infection to spread. CD4 cells, also known as helper T cells, play an important role in cellular immunity by focusing and directing attacks on infected cells so the immune system can accurately and effectively target an infection.

Macrophages promote tissue growth and repair following an injury.
Macrophages promote tissue growth and repair following an injury.

Many microorganisms target the body by attempting to hijack cells. The cell is used to harbor the infectious organism, and some are even capable of repurposing the cell to their own ends, using the cell for reproduction and a source of nutrition. Cellular immunity allows the body to identify cells that have been compromised so they can be destroyed, minimizing an organism's ability to spread through the body.

The immune system uses a series of interconnected systems to catch infectious organisms. One element alone could not eliminate an infection, but by working together, the various aspects of the immune system can effectively target and clean up infectious material, as well as isolating toxins. Destroyed and neutralized infectious material makes it way into the lymph nodes and will eventually be eliminated from the body.

New immune cells are constantly being produced. Every time the body battles an infection, it learns to recognize new infectious material and this information is passed on throughout the immune system so it can respond quickly in the future. The cells involved in cellular immunity must constantly be replenished because many are short-lived and during an active immune response, many of the cells will die.

Most people are only aware of their immune systems when they are not working. The immune system is constantly in action, neutralizing threats before people are alerted to their presence. Sometimes, the system breaks down. Either a microorganism outwits the immune system, or the immune system simply is not capable of dealing with an infection. An infection might be aggressive, spreading faster than the immune system can respond, or new, with the immune system not recognizing it as a threat until it has gained a foothold in the body.

Mary McMahon
Mary McMahon

Ever since she began contributing to the site several years ago, Mary has embraced the exciting challenge of being a wiseGEEK researcher and writer. Mary has a liberal arts degree from Goddard College and spends her free time reading, cooking, and exploring the great outdoors.

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Discussion Comments


@fify-- I think there are a few microorganisms that have been able to evade cellular immunity, like HIV. HIV invades cells and changes its genetic makeup. In a way, it reprograms cells so that it can survive and replicate quickly.

Technically, when this happens, cellular immunity will destroy that cell, but somehow HIV prevents this from happening. Either it replicates too quickly for immune system cells to keep up with it or it somehow prevents immune system cells from functioning. HIV is also known to mutate, so the immune cells probably have difficulty recognizing it as well.

So cellular immunity is not unbeatable, it is not as effective as we think. Some viruses can and are able to beat it.


@burcinc-- Well, yes. If those microorganisms are not contained and destroyed by the immune system, they will spread easily. These microorganism basically use the body's cells. They turn these cells against themselves. It definitely is scary. Thankfully those helper T cells get to work quickly and prevent these microorganisms from causing a full-blown infection.


I didn't know that bad microorganisms can invade the body's cells and use them. That sounds scary. I guess if it weren't for cellular immunity, those microorganisms would take over the body very easily. Am I right?

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