Difference Between Humoral and Cellular Immunity

The difference between humoral and cellular immunity are mainly due to two factors like the type of an immune response and the regulation of immunity.

Type of Immune response: Humoral immunity produces an antibody-mediated immune response, whereas cellular immunity produces a cell-mediated immune response.
Regulation of Immunity: B cell mainly regulates the humoral immunity, whereas T cell regulates cellular immunity.

In this context, we will study the key differences between the humoral and the cellular immunity along with the comparison chart. Also, we will discuss some of the important terms that are frequently used as well as the mechanism of both the immunity systems.

Content: Humoral Vs Cellular Immunity

1. Comparison Chart
2. Definition
3. Mechanism
4. Key Differences
5. Similarities
6. Conclusion

Comparison Chart

Properties	Humoral immunity	Cellular immunity
Definition	It is kind of adaptive immunity that produces antigen specific antibodies to destroy the antigens	It is a kind of adaptive immunity that produces antigen specific T-cells to destroy the antigens
Type of immunity	Antibody-mediated immunity	Cell-mediated immunity
Major role	B-lymphocyte cell	T-lymphocyte cell
Antibody formation	Occurs	Does not occur
Cells involved	B-cell, plasma cell, T-cell, macrophages	TH , TC , NK, macrophage, dendritic cells
Action against pathogen	Destroys the extracellular pathogens	Destroys the intracellular pathogens
Receptors	It involves BCR receptors	It involves TCR receptors
Accessory surface molecules	Igα, Igβ, CD40, cd21 and Fc	CD2, CD3, CD4, CD8, CD28 and integrins
Efficiency of immune response	Rapid	Comparatively slow
Involvement of tumour cells	It can’t eliminate tumour cells	It eliminates the tumor cells thus provides immunity against cancer
Hypersensitivity	It involves immediate hypersensitivity (Type-I, II and III)	It involves delayed hypersensitivity (Type- IV)
Target pathogen	Extracellular bacteria and viruses	Intracellular bacteria, fungi and viruses
Result	It results in the formation of antibodies by the Plasma cells	It results in the formation of cytokines by the T-cell

Definition of Humoral Immunity

Humour means body fluids (like blood and lymph) and Immunity means protection. Thus, we can define it as the active immunity system, in which the antigen-specific antibodies are produced by the B-cells into the body fluids where they provide immunity in counter to the extracellular pathogens by first binding and then neutralizing their activity. Let us discuss a few of the important terms that are frequently used while studying the type of humoral immunity.

Important Terms

B-cell: It is also called B-lymphocytes, which are one of the types of WBCs. B-cells are released by the stem-cell in the bone marrow. The maturation of B-cell occurs in the bone marrow, where it differentiates into the plasma cells. B-cell has a short life span, and it is thymus-independent.

Plasma-cell: It forms by the maturation of the B-cell.  Plasma-cell undergoes cell-division by producing many antibodies in the body fluid. The tendency of plasma cells to produce antibodies is 2,000 antibodies per second.

Endocytosis: It is the process of entrapping the molecules in the extracellular matrix, in which the particles in the surrounding are internalized into the cell via a vesicle formation.

MHC: It stands for Major Histocompatibility Complex. These are the transport proteins that surrounds on the surface of almost all the immune cells and performs a key role in the processing of antigen as well as helps the T-cells in identifying between the self and foreign antigens. Class-I MHC and Class-II MHC are the two common types of major histocompatibility complex.

Definition of Cellular Immunity

As from the name it is clear that this type of immunity is mediated by the cells. Thus, it can be defined as the active immunity, in which the antigen-specific T-cells are produced by the thymus that secretes cytokines to destroy all the intracellular pathogens. Let us discuss some of the important terms that are frequently used while studying the type of cell-mediated immunity.

Important Terms

APCs: It stands for Antigen Presenting Centres. These are the types of cell, which first recognize the foreign body, then engulf it through endocytosis and later form vesicle around the antigen. Then, these APCs will engulf the antigens and neutralize it by forming many fragments. The antigens are then loaded on the MHC after T-cell activation via MHC antigen processing. APCs are of three types, namely dendritic cells, Macrophages and B-cells.

T-cell: In T-cell, T stands for Thymus, which is also a type of WBC that performs a significant role in the immune system. It originates from the thymus via thrombocytes.

T-cell produces more cytokines and undergoes differentiation into many effective T-cells, where each performs a distinct function. There are the following types of T-cells which include:

1. Helper T-cells: It assists the other cells in the immunological processes and called CD4⁺ T cells because they can express the CD4 glycoprotein on their surface. It can also release interleukins that can stimulate the production of B-cells, (NK-cells) natural killer cells, macrophages to destroy the antigens.
2. Cytotoxic T-cells: It is also called Tc-cells, killer T-cells and CD8⁺ T-cell  (expresses CD8 glycoprotein at their surface). It directly destroys the antigen infected cell (mainly virus-infected).
3. Suppressor T-cells: It is also called regulatory T-cells that inhibits T and B-cells.
4. Memory T-cells: It recognizes the pathogen for the future encounter or the second exposure.

Mechanism of Humoral Immunity

Humoral immunity: It involves the following steps:

1. Firstly, the immature stem cells produce B-cells, which then move towards the lymphoid organs.
2. Then, recognition of the antigen takes place with the help of BCR, i.e. B-cell Receptors.
3. The B-cell engulfs the antigen by the process of phagocytosis by forming a phagocytic vesicle around the antigen.
4. After that, the intracellular enzyme (lysozome) fuses with the phagolytic vesicle by forming Phagolysozome.
5. Then this complex phagolysozome digests the pathogen and breaks the antigenic fragments.
6. The antigenic fragments are displayed to the MHC (Major Histocompatibility Complex), which activates the T-cell.
7. Then, the differentiation of B-cells into the mature plasma cells occur with the cooperation of T-cells.
8. Division of plasma cell occurs, which divides to produce its own clones.
9. Then the clones of plasma-cell will produce antibodies specific to the particular antigen. The antibodies will bind and neutralize the antigenic properties of the extracellular pathogens.

Mechanism of Cellular Immunity

Cell-mediated immunity: It involves the following steps:

1. First, the digestion of antigen occurs by the dendritic cell or macrophages. Then the processing of antigen is carried out via MHC.
2. Then, the T-cell gets activated by the MHC-Antigen complex and starts secreting cytokines.
3. The cytokines produced by the T-cell will produce mature T-cells, which then undergo differentiation and form many types of T-cells.
   • Cytotoxic T-cell destroys the cells displaying the antigen.
   • Helper T-cell releases interleukins that stimulate the production of B-cells to produce antibodies, which then binds with the antigen by stimulating the natural killer cells and macrophages.
   • Suppressor T-cell functions to maintain immunological tolerance by inhibiting the activity of other lymphocytes like B and T-cells.
   • Memory T-cell remembers the site of infection or the infected cell for the future encounter.

Similarities

1. Humoral and cell-mediated immunity can generate an antigen-specific immune response.
2. Both humoral and cell-mediated immunity are specific in their action, in which a former produce antigen-specific antibodies and a latter produce antigen-specific T-cells.
3. The immunization of both the kind of immunity (humoral and cellular) is an Active immunization type.
4. The objective of both humoral and cellular immunity is the same, which is to protect the immune system from foreign bodies.

Conclusion

We can conclude that both humoral and cellular immunity are the two different active immunization system, which works on different criteria. Both humoral and cellular immunity is the “Mode switching” process that is carried out by our immune system. When the extracellular pathogens attacks, the immune system of our body switches on the humoral kind of immunity, while the other is switched off.

In the processing of intracellular pathogens, our immune system switches on the cellular kind of immunity by switching off the other. Therefore, the whole process is based on the principle of mode switching, where the immune system recognizes the type of pathogen and regulate the process of immunity with the help of lymphocyte cells.