Passive Acquired Immunity & its Types

Passive Acquired Immunity

Resistance acquired by an individual in the readymade form to fight against infectious agent or toxin from another host. Here, the immune system plays no active role. And it is short-lasting unlike active immunity as it doesn’t produce memory cells. 

TYPES OF PASSIVE ACQUIRED IMMUNITY

 

Natural passive acquired immunity

During the fetal stage, the immunity completely depends on the mother, whether she is vaccinated or not. Since vaccines cannot cross the placental barrier. The fetus receives immunity through IgG. The IgG levels last for about 6 months offering him/her the protection in most vulnerable conditions.

Newborns don't have well-developed immune systems unlike adults. they completely rely on their mother's immunity provided through colostrum, as colostrum contains IgA.

Artificial passive acquired immunity

This type of immunity is given to individual who hasn’t been actively immunized and who has been exposed to an infectious organism. Given by parenteral routes. It acts within a very short span of administration. Artificial passive immunization is given in case of snake bites, diphtheria etc.  and as a specific or non-specific immunosuppressant.

Three different types of immunoglobulin preparations can be used in passive immunization.

 

·      Pooled human serum globulin: 

     It is prepared from the collection of infection-free blood. Then blood is processed to from plasma proteins. Then it is pooled resulting in pooled human serum globulin.

·      Human immunoglobulin: 

    Human immunoglobulin therapy first occurred in the 1930s. It is made from human blood plasma and contains antibodies against many agents like bacteria , viruses, fungi etc.

     Animal antisera: 

  Purified and concentrated preparation of serum of animal that has been actively immunized against a particular infection. Eg for snakes bites anti toxoid vaccines are usually made by injecting a small dosage of venom on horses and gradually increasing the dosage until the horse becomes hyperimmune to that toxin. So that large amount of antivenom could be obtained in short span of time.