Ag Recognition In Adaptive Immunity Flashcards
What is antigen recognition in adaptive immunity?
It is the process by which B and T lymphocytes recognize antigens via specific receptors—B cell receptors (BCRs) and T cell receptors (TCRs).
How do B cells recognize antigens?
B cells recognize native, unprocessed antigens via their B cell receptors (BCRs), which are membrane-bound immunoglobulins.
How do T cells recognize antigens?
T cells recognize processed peptide antigens that are presented on major histocompatibility complex (MHC) molecules by antigen-presenting cells (APCs).
What is the difference between MHC class I and MHC class II?
MHC class I presents endogenous antigens to CD8+ cytotoxic T cells.
MHC class II presents exogenous antigens to CD4+ helper T cells.
What are the different types of immunoglobulin (Ig) isotypes?
IgG, IgA, IgM, IgE, and IgD, each with distinct functions and distributions.
BCRs and antibodies can recognize
linear and conformational epitopes.
TCRs only recognize linear peptides presented on
MHC molecules.
MHC class I molecules bind peptides of 8-10 amino acids, while MHC class II accommodates
longer peptides.
Antibodies mediate immune functions such as
neutralization, opsonization, and complement activation.
CD8+ T cells kill infected cells via cytotoxic mechanisms, whereas CD4+ T cells coordinate
immune responses.
TCRs can recognize free-floating antigens.
False
MHC class I molecules are found on all nucleated cells.
True
Antibodies are part of both innate and adaptive immunity.
False – they are part of adaptive immunity.
BCRs and antibodies recognize the same epitopes.
True
The antigen-binding site of an antibody is formed by ______________ regions.
Variable regions of the heavy and light chains
T cells recognize antigens only when presented by ______________ molecules.
MHC
MHC class II molecules bind to ______________ T cell co-receptors.
CD4
The region of the antibody responsible for biological function is the ______________ region.
Fc
Which type of epitope can be recognized by B cells?a) Only linear epitopes
b) Only conformational epitopes
c) Both linear and conformational epitopes
d) None of the above
Answer: (c) Both linear and conformational epitopes
Which immunoglobulin is the first produced during a primary immune response?
a) IgG
b) IgA
c) IgM
d) IgE
Answer: (c) IgM
Which type of T cell directly kills virus-infected cells?a) CD4+ helper T cells
b) CD8+ cytotoxic T cells
c) B cells
d) Regulatory T cells
Answer: (b) CD8+ cytotoxic T cells
A patient receives a kidney transplant and experiences rejection. What immune molecules are primarily responsible for recognizing the foreign tissue?
MHC molecules, which present antigens to T cells, leading to an immune response against the transplant.
A person with a viral infection has a high number of CD8+ T cells in circulation. What is their primary function in this context?
CD8+ T cells recognize and kill virus-infected cells via MHC class I presentation.
A laboratory test detects high levels of IgE in a patient. What type of immune response is most likely occurring?
An allergic reaction or a parasitic infection, as IgE is involved in mast cell activation and defense against parasites.
Antigen (Ag):
A molecule that triggers an immune response.
Epitope:
The specific region of an antigen recognized by an antibody or TCR.
MHC (Major Histocompatibility Complex):
A protein complex that presents antigens to T cells.
Opsonization:
The process by which antibodies enhance phagocytosis of pathogens.
CDR (Complementarity-Determining Region):
The hypervariable region of antibodies responsible for antigen binding.
