Adaptive Immunity - Complete Study Guide

A comprehensive set of flashcards based on specialized adaptive immunity concepts and key histology markers to aid in exam preparation.

What is the function of CD3?

Part of TCR complex, signal transduction, universal T cell marker.

Which CD marker is found on ALL B cells and is considered the most important B cell marker?

CD19.

What does CD4 function in?

Co-receptor for MHC II and targets for HIV.

What is the role of CD8?

Co-receptor for MHC I and kills infected cells.

What type of cells does CD10 represent?

Immature B cells, marker of early B cell development.

What is the function of CD28 on T cells?

Costimulation receptor; binds CD80/CD86, providing signal 2 for T cell activation.

Which CD marker is the target of Rituximab?

CD20, found on mature B cells.

What structural feature differentiates MHC CLASS I from CLASS II?

MHC I has a heavy chain and β2-microglobulin, while MHC II has two transmembrane chains (α & β).

What peptide binding groove difference exists between MHC CLASS I and MHC CLASS II?

MHC I binds 8-10 amino acids, while MHC II binds 13-25 amino acids.

Where is MHC CLASS I expressed?

On all nucleated cells, excluding RBCs.

What source of peptide do MHC CLASS I molecules present?

Endogenous peptides from inside the cell.

What are the key proteins involved in MHC I loading?

TAP, Tapasin, and Calreticulin.

Which immune cells does MHC CLASS I present to?

CD8+ T cells (cytotoxic T cells).

What does MHC CLASS II primarily present?

Exogenous peptides to CD4+ T cells.

What is the function of HLA-DM in MHC II processing?

Facilitates peptide exchange by removing CLIP from the MHC II groove.

What is the final outcome after TCR recognizes the antigen-MHC complex?

Activation of T cell signaling pathways.

What characterizes positive selection in T cell maturation?

Testing if the TCR can recognize MHC; survival means recognition.

What does negative selection test for in T cell maturation?

If the TCR binds self antigens too strongly; strong binding leads to death.

Which cells do mature T cells exit from?

Thymus.

What enzymes are responsible for V(D)J recombination in T cell development?

RAG1 and RAG2.

What is required for successful somatic hypermutation after B cell activation?

AID (Activation-Induced Deaminase) enzyme.

What is an important role of IgM antibodies?

First antibody produced during primary immune response; best at activating complement.

How does secretory IgA protect mucosal surfaces?

Prevents pathogen attachment and neutralizes toxins.

Which antibody class is primarily involved in allergic reactions?

IgE.

What effect does class switching have on B cells?

Switches from IgM to other types (IgG, IgA, IgE) while retaining antigen specificity.

What does the absence of CD40L lead to in terms of B cell function?

Prevents class switching, resulting in Hyper-IgM syndrome.

What is the primary function of TH1 cells?

Cell-mediated immunity; activates macrophages and fights intracellular pathogens.

What is the primary role of TH2 cells?

Humoral immunity; helps B cells and fights extracellular pathogens.

What cytokine is produced by TH1 cells to help macrophages?

IFN-γ.

What defines the two pathways of B cell activation?

T-dependent activation requires T cell help, while T-independent activation does not.

What happens during T-dependent B cell activation?

B cell binds antigen, processes it, and presents it on MHC II.

What is the result of the germinal center reaction?

Somatic hypermutation and class switching occur.

What is the significance of memory T and B cells?

They provide a rapid and robust response upon re-exposure to an antigen.

What clinical condition results from a defect in AID?

Hyper-IgM syndrome; inability to switch from IgM to other antibody classes.

What triggers mast cell degranulation in type I hypersensitivity?

Allergen cross-links IgE on mast cells.

What type of immune response occurs during the first exposure to an antigen?

Primary response involving naïve T and B cells.

What occurs in the secondary immune response?

Rapid activation of memory B and T cells leading to a quicker and stronger antibody response.

What roles do CD4+ T helper cells play?

Provide help to macrophages and B cells through cytokine signaling.

What does the CD19 marker indicate?

Presence of all B cells; most important B cell marker.

What is the outcome if TAP is blocked during MHC I peptide loading?

No MHC I expression on the surface, leading to detection and destruction by NK cells.

What clinical condition is characterized by low levels of IgG and IgA?

Common Variable Immunodeficiency (CVID).

What is the primary antibody class produced during a secondary immune response?

IgG.

What happens during the affinity maturation process?

B cells with higher affinities for antigens are selected in the germinal center.

What defines the role of CD28?

Costimulation necessary for T cell activation; without it, T cells become anergic.

What are the two mechanisms by which CD8+ T cells kill infected cells?

Perforin/Granzyme pathway and Fas-FasL pathway.

What serves as the 'brake' on T cell activation?

CTLA-4 (CD152), which competes with CD28 for binding.

What does the term autophagy refer to in the context of the immune response?

Process by which cells degrade and recycle cellular components; important for presenting antigens.

How does the immune system recognize foreign pathogens?

Through the detection of pathogen-associated molecular patterns (PAMPs) by innate immune cells.

What is the mechanism of neutralization by antibodies?

Antibodies bind to pathogens or toxins, blocking their ability to interact with host cells.

What is the main characteristic of T-independent B cell activation?

Involves repetitive epitopes leading to weak memory and primarily yields IgM.

What innate immune response triggers the adaptive immune response following injury?

Recognition of PAMPs by macrophages and dendritic cells.

What happens to T cells that cannot recognize MHC?

They do not survive positive selection in the thymus and undergo apoptosis.

What does the presence of high-affinity IgG indicate in the immune response?

A successful and matured adaptive immune response following initial exposure.

What important factor distinguishes live attenuated vaccines?

They replicate and induce a strong immune response compared to inactivated vaccines.

What does the term 'immune exclusion' relate to?

The ability of secretory IgA to prevent pathogen binding to mucosal surfaces.

What causes poor responses to polysaccharide vaccines in children?

Their immune systems primarily function with T-independent responses, leading to weak memory.

What are common features associated with autoimmune conditions driven by TH1 cells?

Crohn's disease and multiple sclerosis.

What defines the relationship between T cells and B cells in adaptive immunity?

T cells help activate B cells, enhancing their antibody production.

How does memory cell response improve upon re-exposure to an antigen?

Faster production and higher affinity antibodies produced due to pre-existing memory cells.

What is the role of the complement system in adaptive immunity?

Enhances opsonization and can lead to lysis of pathogens when activated.

What is the main pathogen that IgG or IgM targets through complement activation?

Bacterial pathogens capable of being opsonized.

What does the 'rusty nail scenario' primarily illustrate?

Integration of innate and adaptive immunity through stages of response to infection.

What is the final outcome of successfully activating the adaptive immune response?

Development of long-lived memory cells leading to robust responses in future infections.

What clinical condition arises from SCID due to RAG deficiency?

Severe Combined Immunodeficiency; no T or B cells, severe infections at infancy.

What role does IL-12 play in T cell differentiation?

Facilitates the differentiation of CD4+ T cells into TH1 cells.

What leads to the destruction of CD4+ T cells in HIV infection?

The direct targeting of CD4+ T cells by the HIV virus.

What effect does the presence of complement proteins have on phagocytosis?

Enhances the ability of phagocytes to recognize and ingest pathogens through opsonization.