Dunn M&C - B Cells (EXTRA-POINTS ON FINAL)

innate immunity

the body's natural, nonspecific, pre-existing first line of defense against infection, present from birth

• recognizes pathogen-associated molecular patterns through pattern recognition receptors (PRRs)

• stimulates the adaptive immune system through cytokine signaling

pathogen-associated molecular patterns (PAMPs)

conserved molecules, unique to microbes and not found in host cells, that signal the presence of a pathogen and trigger immune responses

• lipopolysaccharides, double-stranded RNA, cytoplasmic DNA

pattern recognition receptors (PRRs)

crucial part of the innate immune system, acting as sensors to detect and respond to pathogen-associated molecular pattern

cytokines

small signaling molecules produced by various cells, including immune cells, that regulate inflammation and immune responses

adaptive immunity

specific and long-lasting immune response that develops after exposure

• key components: B lymphocytes and T cells

B lymphocytes

differentiate in bone marrow; produce antibodies, which are symmetrical and bivalent molecules

• expresses one and only one antibody

T cells

differentiate in the thymus; crucial part of the immune system responsible for cell-mediated immunity

thymus

a primary lymphoid organ, crucial for developing and maturing T-cells, a vital part of the immune system

antibodies

proteins produced by the body's immune system to help neutralize or eliminate foreign invaders like bacteria and viruses

• two identical heavy chains and two identical light chains

• two identical antigen-binding sites

• disulfide bonds hold the heavy and light chains together

variable region of antibody

determines antibody specificity, binds antigens

constant region of antibody

doesn’t vary from one antibody to another

• carries out the business of the antibodies

antibody light and heavy chains

generated by genetic recombination (permanent genomic rearrangement)

antibody diversity

generated by a combinations of

(1) DNA rearrangements

(2) somatic hypermutations

somatic hypermutation

purposeful mutations of antibody genes in cells that recognize an antigen to create even more effective antibodies (higher affinity)

• the few produced that are more effective are selected for expansion

clonal selection theory

explains how the immune system selectively amplifies the population of lymphocytes (B and T cells) that recognize and respond to a specific antigen, leading to the development of a specific immune response

• Every B cell expresses one and only one antibody; B cells are activated to proliferate by binding to an antigen

• antigen binding to a resting B cell stimulates it to switch its antibody type to a secreted form

antigen binding to B cells

initiates a signaling pathway that leads to proliferation and survival (cell cycle progression)