The main difference between T cell-dependent and independent antigens is that T cell-dependent antigens require the help of T cells for the activation of B cells. In contrast, T cell-independent antigens do not need the help of T cells for the activation of B cells.
n brief, T-cell dependent and independent antigens are two types of antigens that elicit B-cell response. The activation of B cells may or may not require the help of T cells.
Key Areas Covered
1. What are T Cell Dependent Antigens
– Definition, Features, Importance
2. What are T Cell Independent Antigens
– Definition, Features, Importance
3. Similarities Between T Cell Dependent and Independent Antigens
– Outline of Common Features
4. Difference Between T Cell Dependent and Independent Antigens
– Comparison of Key Differences
T Cell Dependent Antigens, T Cell Independent Antigens
What are T Cell Dependent Antigens
T-cell dependent antigens are the type of antigens that require the help of T cells for the activation of B cells. The majority of T-cell dependent antigens are proteins. They first bind to the mIg on B cells and are internalized by receptor-mediated endocytosis or pinocytosis that is non-specific. These internalized proteins undergo processing by peptidase enzymes in lysosomes, generating peptide fragments that bind to MHC class II molecules. Then, peptide-MHC complexes emerge on the cell surface of B cells, interacting with T cell receptors (TCRs) on helper T cells. Moreover, this release cytokines, directing B-cell proliferation and maturation.
Furthermore, the activated B cells differentiate into plasma B cells that produce antibodies.
What are T Cell Independent Antigens
T cell-independent antigens are antigens that do not require the help of T cells for B cell activation. They are polymeric molecules containing repeating units of antigenic determinants. Therefore, they are multivalent antigens. For example, polysaccharides and polymeric proteins in microorganisms are T-independent polymeric antigens.
Moreover, T-independent antigens cross-link surface receptors of B cells. This tends to produce antigens in B cells by B cell activation. However, without the help of helper T cells, B cells do not produce immunoglobulin isotypes, and therefore, the only form of antibodies produced by B cells is IgM. Hence, T-independent antigens do not produce long-lasting immune responses.
Similarities Between T-Cell Dependent and Independent Antigens
- T-dependent and independent antigens are two types of antigens that elicit immune responses.
- Also, both types of antigens undergo B cell activation.
Difference Between T Dependent and Independent Antigens
T-dependent antigens refer to an immunogen that requires T cell cooperation with B cells to synthesize specific antibodies. In contrast, T-independent antigens refer to typic polysaccharides that can induce B-cell proliferation and antibody secretion in the absence of T cells.
Help of T Cells
T-dependent antigens require the help of T cells to activate B cells, while T-independent antigens do not require the help of T cells to activate B cells.
Most protein antigens are T-dependent, while polymeric molecules with repeated antigenic determinants, such as polysaccharides, are T-independent antigens.
Valency of Antigen
While T-dependent antigens are monovalent, T-independent antigens are multivalent.
T-dependent antigens are fast and require 1-2 days, while T-independent antigens are slower and take several days to initiate a response.
Types of Antibodies
T-dependent antigens react predominantly with IgM, but T-independent antigens react with all Ig isotypes.
Long Lasting Serum Antibody Titers
T cell-dependent antigens produce long-lasting serum antibody titers, while T cell-independent antigens do not produce long-lasting antibody titers.
In brief, T cell-dependent and T cell-independent antigens are two types of antigens that undergo B cell activation. T cell-dependent antigens require the help of T cells to activate B cells. Most T-dependent antigens are proteins, and they are monovalent. Moreover, these antigens quickly initiate immune responses and predominantly react with IgM antibodies. However, T-dependent antigens produce long-lasting serum antibody titers.
In comparison, T cell-independent antigens do not require the help of T cells for the activation of B cells. They are multivalent antigens that slowly initiate immune responses. They react with all types of antibody isotypes. But T-independent antigens do not produce long-lasting immune responses. Therefore, the main difference between T-dependent and T-independent antigens is their requirement for T cells to activate B cells.
- Thymus dependent antigen. ScienceDirect Topics.