I’m confused, because the definition of acquired immunity states:
‘ Exposure to pathogen triggers the 3rd line of defence to produce **antibodies** for that pathogen’
Doesn’t this definition kind of ‘disregard’ the immunity that develops in response to an intracellular pathogen (ie. when we need Tc Cells for cell mediated response)?
In: Biology
There’s cell mediated (T cells) vs humoral (B cell) immune responses. The general effects of getting sick (fever, fatigue) often come from cytokines released by T cells. These are often specific to pathogen type, though their memory response can be activated by a specific pathogen. Mature B cells secrete Antibodies, and are often activated by T cells
Simply: No.
Antibodies are made as part of the humoral response. They are not part of the cell mediated response, but they can be produced _as a result_ of the cell mediated response. They do help with the cell mediated response by ‘flagging’ things for destruction, but are not needed for it.
The reason they may be ‘disregarding’ the T cell immunity is because this T cell activation normally happens before B cell activation.
Basically cell mediated means ‘fought mostly by cells’ and humoral response means ‘fought with chemicals’. Cells being all manor of T cells and phagocytes, and chemicals being antibodies.
Actually, the reverse is true: cell-mediated responses are generally needed for antibody secretion to occur.
For humoral (B cell) immunity, a certain subset of CD4+ T helper cells, known as T follicular helper cells (Tfh) are required to activate naïve B cells via a MHC class II-TCR interaction. Once the naïve B cell is activated, it can differentiate into high/low-affinity secreting plasma cells which are then responsible for secreting antibodies (namely IgG, IgA, and IgM). Affinity of the antibody depends on whether the B cell undergoes class switching/somatic hypermutation in the germinal center of a secondary lymphoid tissue. **So, in fact, cell-mediated immunity is required for antibody secretion to occur.**
Note: this only applies to an immune response to a **protein** antigen. Humoral immunity in response to a non-protein antigen can occur independent of an activating Tfh cell, and thus independently of cell-mediated immunity.
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