Adaptive Immunity: Key Cells, Development, and Immunoassays

What is adaptive immunity?

A specific immune response to each pathogen or antigen, characterized by immunological memory for faster responses upon re-exposure.

What are the central players in adaptive immunity?

T lymphocytes (T cells) and B lymphocytes (B cells).

What is the role of T helper cells (Th)?

They assist other immune cells and interact with MHC II.

What distinguishes cytotoxic T cells (TC)?

They express CD3+ and CD8+ and are responsible for killing infected or abnormal cells.

What is the significance of regulatory T cells (Treg)?

They suppress autoimmunity and maintain immune tolerance by secreting inhibitory cytokines.

What occurs during the double negative stage of T cell development?

Thymocytes are CD4- and CD8-, and gene rearrangement for the TCR chain begins.

What happens during the positive selection of T cells?

It ensures that TCR can bind to host MHC, allowing survival of thymocytes.

What is the outcome of negative selection in T cell development?

It eliminates thymocytes whose TCR bind strongly to self-antigens.

What is the differentiation pathway of B cells?

B cells originate from hematopoietic stem cells in the bone marrow and go through stages: Pro-B cells, Pre-B cells, Immature B cells, and Mature B cells.

What is central tolerance in B cell development?

It eliminates B cells whose IgM receptors bind strongly to self-antigens through apoptosis.

What are the two phases of B cell activation?

The antigen-independent phase (differentiation) and the antigen-dependent phase (activation and class switching).

What is the difference between T-dependent and T-independent antigens?

T-dependent antigens require help from Th cells for memory cell formation, while T-independent antigens lead to IgM production with little or no memory.

What is serology?

The study of blood fluids, especially antibodies.

What is the purpose of flow cytometry?

To distinguish T-cell and B-cell subsets based on surface markers, useful in diagnosing immune disorders.

What is the significance of the dilution factor in serial dilutions?

It determines the concentration of solute in each successive dilution step.

What is the titer in the context of immunology?

The highest dilution at which a positive reaction is still observed, reported as the reciprocal of the dilution.

What is the principle of agglutination assays?

Antibodies bind particulate antigens to clump them, indicating a positive reaction.

What distinguishes direct agglutination from passive agglutination?

Direct agglutination uses native particulate antigens, while passive agglutination uses inert particles coated with antigens.

What is the role of labeled immunoassays?

To detect antigens or antibodies, especially when present in low concentrations, using labels like fluorescent or radioactive tags.

What is the difference between competitive and noncompetitive immunoassays?

In competitive assays, labeled and unlabeled antigens compete for binding sites, while in noncompetitive assays, a labeled antibody detects bound antigen.

What are the advantages of homogenous assays?

They do not require a separation step, making them simpler and faster, but generally less sensitive.

What is the significance of the zone of equivalence in precipitation assays?

It is the optimal ratio of antigen and antibody where maximal lattice formation occurs.

What is the principle behind immunoelectrophoresis?

Proteins are separated by electrophoresis, and then antiserum is allowed to diffuse to form precipitin arcs.

What is the purpose of chemiluminescent immunoassays?

To provide high sensitivity and faster results by emitting light through a chemical reaction.

What is the function of antibodies in immunoassays?

They bind specifically to antigens, allowing for detection and quantification of immune responses.

What is the role of cytokines in B cell class switching?

Cytokines drive the process of class switching, enabling B cells to produce different antibody isotypes while maintaining antigen specificity.