To stay healthy, every multi-cellular organism has its own defense mechanism to fight against the foreign cellular organism that invades the body. This mechanism is otherwise called as immunity. Immunity is an intricate mechanism present in our body which identifies the self and the foreign materials. It readies the body to fight against the foreign material and restore the normalcy in the body. There are different types of immunity mechanism present in our body. Adaptive and innate are two main types of immunity. The adaptive immune system consists of several specialized cells which prevent the growth of pathogens and destroys the pathogen.
Innate immunity is the primary line of defense against bad micro-organisms and eliminates the infection. Out of different types of immunity, humoral and cell-initiated immunity are the two major mechanisms in the adaptive immune defense system. Humoral immunity is a category of immunity that is intervened by macro-molecules and anti-bodies present in body fluids outside the cells. It is also called an antibody-mediated immune system as antibodies act as a primary defense mechanism in establishing immunity. These antibodies are produced by a specific type of cells. Cell-initiated or cell-mediated immunity is also a part of the adaptive immune system.
It protects the body from pathogens that have entered or invaded into a body cell. The response in Cell-mediated immunity is not mediated by antibodies. Rather the defense mechanism is achieved with the help of receptors to detect the antigens.
Humoral vs Cell-Mediated Immunity
The main difference between humoral and cell-mediated immunity is that in humoral immunity, the response is an antibody-mediated one. But in case of cell-mediated immunity, cytokines are responsible for the defense mechanism in the body. Humoral immunity fight against antigens that are free-floating in the body fluids. Cell-mediated immunity acts against the antigen that are entering the body cells.
Comparison Table Between Humoral and Cell-Mediated Immunity
|Parameters of Comparison||Humoral Immunity||Cell-Mediated Immunity|
|Definition||Humoral Immunity protects the body against pathogens and antigens that are freely floating inside our body.||Cell-Mediated Immunity fights against various pathogens that invade the cells (intracellular pathogens).|
|Mechanism||The immune response is mediated by the antibodies produced mainly by B-lymphocytes, macrophages and T-lymphocytes.||The immune response is mediated by the release of cytokines, cytotoxic T-lymphocytes, natural killer and helper T-cells.|
|Secretion||It releases antibodies||It releases cytokines|
|Function||The B-cells produce antibodies which bind and detects the antigen.||The T-cells receptors are responsible for detection and binding to the antigen.|
|Fight Against||Extracellular bacterial and virus pathogens||Intra-cellular bacterial and pathogens|
|Hypersensitivity||Hypersensitivity type I, II and III are mediated by the humoral immune system.||Cell-mediated immunity mediates hypersensitivity type IV.|
What is Humoral Immunity?
Humoral cell immunity is one of the major types in the adaptive immune system. The immune response in humoral immunity is mediated or governed by antibodies produced by B-lymphocytes. The B-lymphocyte cells identify the antigen or the free-floating foreign substance present in the body fluids (blood/lymph). As soon as the plasma B-lymphocytes detects the free-floating foreign material, they produce suitable antibodies which get bind to the specific antigen (foreign substance). Then the antigen gets neutralized and antibodies destroy the antigen by lysis or phagocytosis.
Macrophages and T-helper cells also assist the immune system by helping the B-lymphocytes to activate plasma B-lymphocyte cells as soon as the antigen is detected. These activated plasma cells carry antigen-specific antibodies which get bind to the pathogen and lysis takes place. Memory cells are produced after the destruction of the antigen by the same B-lymphocytes. These memory cells would be responsible for future immunity when the same antigen is detected in the body again.
It should be noted that the initial stage of graft rejection is associated with humoral immunity due to the development of antibodies against the pathogen. And the immune response is rapid when compared to cell-mediated immunity.
What is Cell-Mediated Immunity?
Cell-Mediated Immunity is another type in adaptive immunity where the immune response is mediated by T-lymphocytes, cytotoxic and other natural and helper T cells. Cell-mediated immunity acts against the antigen or pathogens that invade the cells. Basically, the cell-mediated immune response is to fight against fungi, intracellular bacterial pathogens and virus. In the case of cell-mediated immunity, it is not governed by antibodies. Instead, it is mediated by T-lymphocytes receptors.
Cytokines are released by helper T-cells which will trigger the T-lymphocytes. Then, the T-cells get bind to the antigen and gets differentiated into cytotoxic T-cells. This would initiate the lysis of the cell and thus the antigen gets destroyed. This immune system is specifically for intracellular pathogens. This immune response is associated with the rejection of organ transplant. Though the response is slow when compared with humoral immunity, it leaves a permanent and long-lasting impact.
Main Differences Between Humoral and Cell-Mediated Immunity
- Humoral immunity is mediated or intervened mainly by antibodies produced by B-lymphocytes whereas cell-mediated immunity is mediated by the production of cytokines from T-lymphocytes.
- To detect antigens, antibodies are employed in humoral immunity. In the case of cell-mediated immunity, receptors are responsible for the detection of antigens.
- Antibodies are formed only in humoral cell immunity and not in cell-mediated immunity.
- Humoral cell immunity helps to fight against free-floating extracellular pathogens whereas cell-mediated immunity helps to fight against intracellular bacterial pathogens.
- Antibodies produced by the humoral immunity binds to the antigen. But in cell-mediated immunity, T-cells gets bind to the foreign substance (antigen) and get differentiated into the cytotoxic cell.
- Hypersensitivity (I, II, III) is governed by humoral immunity whereas cell-mediated immunity provides hypersensitivity IV.
- Medical research had found that cell-mediated immunity (not humoral immunity) has the potential to eradicate tumour cells.
Though humoral and cell-mediated immunity belongs to the adaptive immune system, they have a major difference in the way they function. While antibodies are responsible for immune response in humoral immunity, cytokines are responsible for the defense mechanism in cell-mediated immunity.