lecture 1: immune system and adaptive immunity

What is the overall function of the immune system? what does it keep record of?

prevent or limit infection

every antigen it encounters

What type of stem cell gives rise to all cells of the immune system?

what 2 types of cells are developed further from that?

pluripotent stem cell

common lymphoid progenitor and myeloid progenitor

what type of immunity is associated with and what type of cells are produced from the common lymphoid progenitor?

adaptive immunity

T cells, B cells, NK cells - (NK cells made with same progenitor but are innate)

what types of immunity is associated with and what type of cells are produced from the myeloid lineage?

innate immunity

phagocytes (neutrophils, basophils, eosinophils, and mast cells) and antigen-presenting cells (dendritic cells, macrophages)

where do lymphocytes (B and T cells) originate and develop? what else occurs here?

bone marrow

B cells mature here

where do T cells mature?

thymus

what are the primary lymphoid organs?

bone marrow and thymus

What are some secondary lymphoid organs? what happens here?

tonsils, lymph nodes, appendix, spleen

lymphocytes interact and generate immune responses to antigens

What is the function of secondary lymphoid organs in relation to antigens?

They trap and concentrate foreign materials and expose these materials to lymphocytes

What is the function of the spleen in the immune system?

To process antigens in the bloodstream and filter the blood

What is the significance of antigen-specific receptors on immune cells?

They allow T cells and B cells to recognize and respond specifically to antigens

What is the main function of the lymphatic system related to immunity?

It facilitates immunity by carrying antigens and antigen-presenting cells to interact with lymphocytes

What is the significance of the complement cascade in the immune response?

It is part of the innate immune response and can be activated by antibodies, illustrating crosstalk between innate and adaptive immunity

characteristics of adaptive immunity

has memory, responds differently to novel versus previously encountered antigens, takes longer to activate (days to weeks), discrimination of self/nonself, clonal selection

major cell types of adaptive immunity

B cells, T cells, APCs

What is the difference between humoral immunity and cellular immunity in the adaptive immune response?

Humoral immunity is predominantly mediated by B cells and their antibodies, while cellular immunity involves T cells

what is the basis for immunizations and the hallmark of the adaptive immune system?

clonal expansion of lymphocytes

the rapid proliferation of B/T cells from one or a few activated cells into large populations of identical cells that have the same antigen receptor

characteristics of innate immunity

includes physical barriers and internal defenses, has a rapid response time (minutes to hours), and does not have a memory response

What is the role of T cells in the immune system?

They produce cytokines that communicate with other cells, including B cells and macrophages

How does clonal expansion relate to immunizations?

immunizations activate a small number of B cells, leading to the clonal expansion of antibody-producing B cell

What are helper T cells and how do they function?

They express CD4+ and communicate with other immune cells via cytokines to enhance the immune response

What are killer T cells and their role in the immune system?

They express CD8+ and directly kill infected or cancerous host cells

What is the function of regulatory/ suppressor T cells?

they are specialized CD4+ cells that regulate the immune response by signaling other immune cells to stand down

these cells alert the body of the "self"

What are memory T cells?

specialized T cells that provide long-term immunity by remembering past infections

either CD8+/4+

What is the role of antigen presenting cells (APCs) in the adaptive immune response?

APCs present antigens to T cells, initiating the adaptive immune response

What is the role of B cells in the immune response?

they generate antibodies in response to antigens

(they recognize antigens and respond by differentiating into plasma cells that produce antibodies (immunoglobulins) to neutralize pathogens, and memory B cells that provide long-term immunity)

What is the function of plasma cells?

specialized B cells that produce and secrete antibodies

What is the primary characteristic of memory B cells?

long-lived and primarily preserve genetic info to respond to specific antigens

How do plasma cells differ from memory B cells in terms of structure?

Plasma cells have a large cytoplasm filled with endoplasmic reticulum for antibody production, while memory B cells are smaller with a larger nucleus

What distinguishes humoral immunity from cell-mediated immunity?

humoral: B cells and the antibodies they produce in the plasma

cell-mediated: mediated by t-cells. targets infected cell

Humoral = B cells + antibodies → attack pathogens in fluids

Cell-mediated = T cells → attack infected cells directly

What are BCRs and TCRs and what are they responsible for?

unique antigen receptors expressed on the surface of lymphocytes

BCRs recognize and bind to intact antigens, while TCRs recognize antigens presented on MHC molecules

What is the role of the antigen binding site in BCRs?

The antigen binding site allows BCRs to interact with free-floating antigens

What happens to B cells when they are activated?

they can differentiate into plasma cells and secrete antibodies with the same specificity as the BCR

What is the role of the antigen binding site in T cell receptors?

The antigen binding site on TCRs recognizes peptide antigens presented on MHC molecules

[The virus stays inside the infected cell.

The infected cell chops up viral proteins into small pieces (peptides).

These peptides are placed on the MHC molecule on the cell surface.

T cells recognize the MHC + viral peptide combo and respond:

CD8+ T cells → kill the infected cell.

CD4+ T cells → help activate B cells or other immune cells]

What occurs when a T cell receptor binds to its specific peptide-MHC complex?

It triggers a signal cascade inside the T cell, leading to activation, proliferation, and various functions (helper, memory, regulation, killer)

What is a unique feature of each B cell and T cell regarding their receptors?

Every B cell and T cell expresses its own unique receptor; for example, B cell 1 produces BCR1, and T cell 2 produces TCR2

What are epitopes?

the specific parts of an antigen that interact with antibodies

What happens to auto-reactive B cells during clonal selection?

They are removed from the population to prevent the immune system from attacking the body's own tissues

What happens when a B cell receptor binds to its specific epitope?

The B cell is stimulated to divide and produce antibodies specific to that epitope

What is apoptosis and which cells induce it?

programmed cell death, induced by cytotoxic T lymphocytes in infected or cancerous cells

What is the role of a B cell when it encounters its corresponding antigen?

The B cell matures into a plasma cell, producing large amounts of antibodies targeting the antigen, and also generates memory B cells

What is the function of helper T cells in B cell activation?

Helper T cells provide necessary signals through cytokines to fully activate B cells for antibody secretion

What are the three main functions of antibodies in the immune response?

Antibodies can neutralize pathogens, opsonize pathogens for phagocytosis, and activate the complement cascade

What is the significance of naive T and B cells?

Naive T and B cells are in a developmental state where they have not yet encountered an antigen and are not actively producing antibodies

What is the first signal required for T cell activation?

The interaction between the MHC displayed antigen and the T cell receptor

What provides the second signal necessary for T cell activation? What do they do?

Co-stimulatory molecules from antigen presenting cells

They fine-tune the first signal and control the growth, differentiation, and function of the responding T cell