The key difference between humoral and cell mediated immunity is that the humoral immunity (antibody-mediated immunity) involves antibodies while the cell mediated immunity does not involve antibodies.
Immunity is the ability of an organism to defend against pathogens and toxins and to avoid infections and diseases. Therefore, the immune system is the tissue system that controls our immunity. It comprises primarily of individual cells spread throughout the body. Thus, the immunity can be two types; innate immunity or adaptive immunity. Adaptive immunity is a synonym for specific immunity, which provides pathogen-specific immunity in vertebrates. Moreover, this adaptive immune system basically composes of T-lymphocyte and B-lymphocyte cells. And it is is very special as it is present only in vertebrates, and is able to recognize different foreign antigens in a very precise way.
According to the composition of the adaptive system, it can be further divided into two categories; humoral immunity and cell-mediated immunity. Humoral immunity is the primary defence system against extracellular pathogens which drives by the B lymphocytes. On the other hand, cell mediated immunity is the primary defence system against intracellular pathogens which drives by the T lymphocytes.
CONTENTS
1. Overview and Key Difference
2. What is Humoral Immunity
3. What is Cell Mediated Immunity
4. Similarities Between Humoral and Cell Mediated Immunity
5. Side by Side Comparison – Humoral vs Cell Mediated Immunity in Tabular Form
6. Summary
What is Humoral Immunity?
Humoral immunity, also known as antibody-mediated immunity, is one branch of adaptative immunity that mediates by antibodies secreted by the B- lymphocyte cells. Humoral immunity works against specific pathogens outside the cells (extracellular pathogens). B-cells are bone marrow-derived, and each cell makes only one kind of antibody which specifically reacts on a particular pathogen. DNA rearrangement makes sure the antibody diversity.
Figure 01: Humoral Immunity
Moreover, these antibodies can directly neutralize viruses. For certain pathogens, the antibodies bind to target the cells and signal phagocytes or other white blood cells or other defence mechanisms to attack them. Thus, B cell activation, B cell proliferation and antigen-antibody interaction are three main mechanisms of humoral immunity.
What is Cell Mediated Immunity?
Cell mediated immunity is the immunity that mediates by T-cell antigen receptors made by thymus-derived T-cells. As the name implies, T-cells themselves specifically bind with the antigens, instead of releasing the receptors from the cell body. However, there is no antibody involvement in cell mediated immunity. Furthermore, cell mediated immunity works mainly for intracellular pathogens. Cell mediated immunity is mainly facilitated by the T helper cells and cytotoxic T lymphocytes.
Figure 02: Cell Mediated Immunity
Each T-cell makes only one kind of T-cell antigen receptor. Thus, the t-cell receptor has four proteins, namely, two large (α) and two small (β) chains. Each chain has constant and variable regions. The variable regions determine the specificity of the receptor toward a particular pathogen while the variable regions project outside helping to bind the T-cells to the antigen cell. Thus, the cell-mediated immune system is important as it eliminates tumour cells before they can grow and spread very much. This process is known as ‘immunological surveillance’. Also, when tissue from an unrelated individual is introduced into another individual, this immune system will respond and kill the transplanted tissue immediately.
What are the Similarities Between Humoral and Cell Mediated Immunity?
- Humoral and Cell Mediated Immunity are two types of adaptative immunity.
- Both immunity types activate upon the exposure to foreign antigens.
- They effectively defence our body against a variety of pathogens.
- Also, both immunities create immunological memory against antigens.
- Besides, they both systems do not work properly in immune-compromised people.
What is the Difference Between Humoral and Cell Mediated Immunity?
The key difference between humoral and cell mediated immunity is the production of antibodies. Humoral immunity mediates by the antibodies produced by B lymphocytes while cell mediated immunity does not involve antibodies. Furthermore, humoral immunity mainly works against extracellular pathogens identified by the antibodies while cell mediated immunity works against intracellular pathogens identified by the T cell receptors. Hence, this is also a difference between humoral and cell mediated immunity. Another important difference between humoral and cell mediated immunity is that the humoral immunity does not provide immunity against cancers while the cell mediated immunity provides immunity against cancers.
The below infographic presents a more detailed analysis of the difference between humoral and cell mediated immunity.
Summary – Humoral vs Cell Mediated Immunity
Humoral and cell mediated immunity are two types of active or adaptative immunity. The key difference between humoral and cell mediated immunity is that the humoral immunity facilitates by the antibodies produced by B lymphocytes. In contrast, cell mediated immunity does not facilitate by the antibodies. It is mediated by TH cells and cytotoxic T lymphocytes. Another difference between humoral and cell mediated immunity is that the humoral immunity works against extracellular antigens while the cell mediated immunity works against intracellular antigens.
Reference:
1.“Humoral Immunity.” Wikipedia, Wikimedia Foundation, 8 Sept. 2018. Available here
2.Janeway, Charles A, and Jr. “T Cell-Mediated Immunity.” Current Neurology and Neuroscience Reports., U.S. National Library of Medicine, 1 Jan. 1970. Available here
Image Courtesy:
1.”B cell activation”By Fred the Oysteri (Public Domain) via Commons Wikimedia
2.”T cell activation”By Hazmat2 – Own work, (Public Domain) via Commons Wikimedia