The immune response is the process by which your body protects itself against germs, microorganisms and foreign substance that are harmful to your body. More formally speaking, it is the protective mechanism triggered by your body in response to antigens.

An antigen is any substance that triggers an immune response; i.e., any substance that causes your immune system to produce antibodies.

Primary and Secondary Immune Response

Primary immune response is the first response that your body initiates immediately a pathogen or a foreign object enters into the cells. In the first few days, there’s little viable response from the body. The presence of the foreign antigen triggers the T-helper cells, which continue the sequence involved in initiating the immune response. This involves the division of T and B cells, followed by the activation of plasma cells. These cells secrete antibodies in adequate numbers to render the antigen harmless.

The secondary immune response occurs once the body “stores memory of certain pathogens” in the T-cells and memory B-cells and develops antibodies for the specific antigen. The secondary immune response is triggered when this specific pathogen or antigen enters the body. Immediately, the memory B-cells quickly segregate into plasma cells. The levels of antibodies also increase rapidly. The antibodies then quickly neutralize the invading pathogens.

Types of Immunity

There are three types of body immunity. This includes the innate immunity, passive immunity and acquired immunity.

  • Innate immunity is also known as natural immunity. You are born with this kind of immunity which keeps harmful substances from penetrating your body. This immunity involves barriers that form the first line of defense in the immune response such as the mucus, cough reflex, stomach acid and enzymes in tears. The immune system attacks and obliterates an antigen when it gets past the external barriers.
  • Passive immunity is the immunity that is found in the infants. Infants are born with antibodies which are transmitted from the mother through the placenta. The antibodies disappear within a period of 6 to 12 months of age. Passive Immunization involves transfusion of antiserum, which is produced by another person or an animal resistant to a certain pathogen, hence providing immediate defense against an antigen. An example of passive immunization is the equine (horse tetanus antitoxin) and the Gamma globulin.
  • Acquired immunity is the immunity that is developed when the pathogens are able to elude innate immune defenses. A resistance is built that is definite to that antigen due to the exposure to various antigens. The components of this type of immune response are usually silent.


The immune response is activated through immunization (vaccination). To activate immune system “memory”, small doses of an antigen are provided. Such antigens include weakened or dead viruses or pathogens. Memory (sensitized T-cells and triggered T-cells) enables your body to respond rapidly and effectively to the future exposure of the live form of the pathogen.

Allergies and Immune System Disorder

The immune system disorder develops when the immune response is wanting, inappropriate or excessive. This means that your body attacks and destroys its own cells, or that it fails to trigger sufficient response to counter an antigen. Immune deficiency diseases such as AIDS weaken your body’s capacity to fight foreign substances, making you vulnerable to other diseases that you normally are immune to. Allergies occur when there is an immune response to foreign substances that is perceived harmless by the body.

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