The main difference Between Humoral and Cell-mediated Immunity is in the mechanism of immunity, in which Humoral immunity produces antibodies against antigens that are either outside the infected cells or circulate freely in the blood. Cell-mediated immunity acts inside infected cells, where it destroys pathogens or microorganisms through the process of lysis by the release of cytokines.
Humoral immunity exhibits a rapid response to pathogens, while cell-mediated immunity is slow in action. Both types are part of the adaptive immune system. Our immune system provides protection and resistance against infectious diseases, offered by the host cells present in the body.
The immune system has a complex network of molecules, cells and their interactions designed to eradicate infectious organisms from the body. The immunity or immune system is divided into two types – innate (non-specific) and acquired or adaptive (specific) immunity.
Innate immunity acts as a defensive barrier and represents an organism’s ability to protect against disease. On the other hand, acquired immunity represents the most powerful line of defense mechanism in the body, which is known to identify and destroy any specific pathogens or foreign particles that are harmful to the body.
Acquired or adaptive immunity displays four main characteristics, such as Recognition diversity; Immunological memory; antigen specificity; and Discrimination among self and non-self.
In this content, we will study Humoral and cell-mediated immunity, which are part of adaptive or acquired immunity. We will also focus on the points that distinguish these terms, with a brief summary.
Definition of Humoral Immunity
The humoral immune response or antibody-mediated response is associated with B cells, where the role of these cells (B cells) is to identify antigens or foreign particles present in the circulation in the blood or lymph. This immune response is also assisted by helper T cells which together with B cells differentiate into plasma B cells that can produce antibodies.
Once B cells produce antibodies, they will bind to the antigen; neutralize them and cause phagocytosis or cell lysis (cell destruction). An antigen is a foreign particle, which is usually a carbohydrate or protein that triggers an immune response, but on top of that our bodies have an amazing ability to identify antigens.
Exposure to any antigen leads to the development of a secondary immunological response that increases the level of the immune response. Immunoglobulins or antibodies mediate humoral immunity, these are a specific group of proteins produced by B-lymphocytes.
The following points can explain the final process:
- Antigen triggers to the body.
- The antigen binds to B cells present in circulating blood.
- Helper T cells or Interleukins assist B cells and initiate B cell proliferation which activates plasma B cells.
- Plasma cells carry antigen-specific antibodies and have specific binding receptors on activated B cells.
- These antibodies travel throughout the body and bind to antigens.
- B cells after destroying the antigen, produce memory cells which in turn provide immunity in the future when the same antigen triggers the body again.
Definition of Cell-Mediated Immunity
T lymphocytes help cellular immunity or cellular immunity. In this type, cytokines have been released which help activate the T cells which further destroy the infected cells. Likewise B cells, T cells originate from the bone marrow but mature in the thymus and then circulate in the bloodstream and lymphoid tissues.
Antigens are present on the surface of antigen-presenting cells (APCs) with abnormal Major Histocompatibility Complex (MHC) proteins. Abnormal or aberrant MHC molecules are formed from antigens that have been destroyed or cleaved or from infected viruses (exogenous antigens) or from tumor cells that are actively producing foreign proteins (endogenous antigens).
Now the helper T-cells release cytokines, which will activate the T-cells, which will recognize the aberrant MHC antigen complex and will bind to it and differentiate into cytotoxic T-cells. After this the cell will undergo lysis (cell destruction).
The following points can explain the final process:
- Antigen-presenting cells (APCs) will display antigens on their surface and bind to T cells.
- Interleukins (secreted by helper T cells) facilitate T cell activation.
- Along with MHC-I and endogenous antigens, T cells proliferate and produce cytotoxic T cells.
- T cells destroy infected cells showing antigens.
- In the case of exogenous antigens and MHC-II displayed on the plasma membrane together, T cells trigger the proliferation of helper T cells that release interleukins and cytokines and also excite B cells to produce antibodies against them. This process is also supported by natural killer (NK) cells and macrophages, which destroy antigens.
Key Differences between Humoral and Cell-Mediated Immunity
Following are the main points showing the difference between Humoral and Cell-mediated Immunity:
- Humoral immunity is associated with B-lymphocytes and is responsible for destroying pathogens by producing antibodies against it, whereas cell-mediated immunity is associated with T-lymphocytes and is responsible for destroying pathogens or microorganisms that have invaded cells without producing antibodies.
- Humoral immunity is closely related to B-lymphocytes, T-lymphocytes, and macrophages, in contrast, cell-mediated immunity is associated with T-lymphocytes, helper T cells, natural killer cells, and macrophages.
- Humoral immunity plays a major role in recognizing any antigen or foreign particle and in producing antibodies against it. It is known to work against extracellular pathogens.
- Cell-mediated immunity is associated with T-lymphocytes, which work by identifying viruses and microorganisms, thereby destroying them by cell lysis or phagocytosis or pinocytosis. It is known to work against intracellular pathogens.
- Humoral immunity secretes antibodies against antigens, whereas cell-mediated immunity secretes cytokines and no antibodies against pathogens.
- Humoral Immunity is fast or fast in its action against antigens, while cell-mediated immunity shows a delay in spite of permanent action against any pathogen.
- Humoral immunity mediates type I, II, and III hypersensitivity, whereas cell mediation is delayed in response and mediates type IV hypersensitivity.
- Humoral immunity is involved in the early stages of graft rejection due to the formation of antibodies against foreign particles, while cell-mediated immunity is involved in rejection of organ transplants after a certain time as it exhibits a delayed response.
Conclusion: From the above content, we got to know about some critical differences between the two types of active immune system which are cell-mediated and cell-mediated immune responses. We conclude that the two types of immunity differ in the process of destroying pathogens, wherein antigen-specific antibodies are rapidly produced against the antigen, while in cell-mediated immunity, pathogens are destroyed via cell lysis.
