Are antibodies needed for cell mediated response?

Question

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

Answer 1

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.**

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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.