Biotechnology: Antibodies & their role in Therapeutics

Describe the basic structure of immunoglobulins, two light and two heavy chains held by disulfide bonds, forming a Y-shaped molecule with variable regions creating two antigen binding sites.

Learn Fab and Fc structure; papain and pepsin digestion reveal fragments, while mercaptoethanol shows two heavy and two light chains linked by disulfide bonds for opsonization and complement activation.

Describe the antibody as a y-shaped molecule with two heavy chains and two light chains linked by disulfide bonds, bearing carbohydrate attachments and two Fab regions, plus an Fc stem.

Examine the light and heavy antibody chains and their amino acid sequences. Learn why homogeneous antibodies enable sequencing and how multiple myeloma yields abundant, uniform antibodies with Bence-Jones proteins.

Examine the five heavy-chain isotypes—delta, gamma, alpha, mu, and epsilon—and how their constant regions define antibody classes IgD, IgG, IgA, IgM, and IgE. Explore subclasses IgA1/IgA2 and IgG1-4.

Explore immunoglobulin domains from primary amino acid sequences to the immunoglobulin fold and quaternary assembly, detailing heavy and light chains, variable and constant domains, beta sheets, and disulfide bonds.

Examine complementarity determining regions (CDRs) in heavy and light chain variable domains that form the antibody antigen-binding sites, with six CDRs per site shaping specificity.

In antibody variable domains, heavy and light chains have cdrs as antigen binding sites and conserved framework regions that act as a scaffold to position cdrs for antigen contact.

Complementarity-determining regions form the antibody's antigen binding site and determine specificity by matching epitopes. Large antigens contact broad surfaces; heavy and light chains together define specificity.

Explore the hinge region of antibodies, its role in enabling Fab mobility and antigen interaction, and how proline and cysteine influence proteolysis and disulfide bonding across Ig classes.

Summarize the detailed antibody structure, including light chain types (kappa or lambda), heavy chain isotypes (IgD, IgG, IgA, IgM, IgE), variable and constant domains, CDRs, and hinge regions.

IgG is the most abundant serum antibody, with four subclasses differing in hinge size and disulfide bonds; it crosses the placenta and activates complement, supporting fetal protection and pathogen clearance.

IgA1 and IgA2 differ in hinge length, forming secretory IgA. Secretory IgA is polymeric, carries a J chain and secretory component, providing defense at mucosal surfaces.

IgE is a monomeric antibody with two heavy and two light chains, present at 0.3 μg/ml. It mediates defense against parasites and allergic reactions via mast cell and eosinophil degranulation.

Explain the five antibody classes—IgG, IgA, IgM, IgE, and IgD—their monomeric or polymeric forms, J chain involvement, and their roles in placental transfer, complement activation, opsonization, and mucosal defense.

Explore the complement system, its activation pathways and enzyme cascade that enhances antibodies and phagocytes to clear microbes and damaged cells, including heat-labile and heat-sensitive components.

Complement proteins C1–C9 circulate inactive and activate by cleavage into a and b fragments; C2 is exception, with fragments activating and forming complexes, while smaller fragments diffuse to inflammation.

Explore the classical pathway of complement activation triggered by antigen-antibody complexes (IgM and IgG), revealing C1 activation, C3 convertase, C5 convertase, and MAC initiation via C5b.

Explore how the alternative pathway of the innate immune system activates complement without antibodies, forming C3 convertase (C3bBb) stabilized by properdin, then C5 convertase to drive membrane attack complex formation.

Understand the lectin pathway of complement activation initiated by mannose-binding lectin binding to microbial surfaces. MASP-1/2 activate C4 and C2 to form C3 and C5 convertases and membrane attack complex.

The classical, alternative, and lectin pathways converge to form the membrane attack complex (MAC), which inserts into the target cell membrane and creates pores that lyse pathogens.

Explain how the classical, alternative, and lectin pathways activate the complement system to form C3 convertase, then C5 convertase, and the membrane attack complex that lyses target cells.

Explain how the complement system defends against pathogens while protecting host cells through three regulatory stages and key inhibitors like C1Inh, RCA proteins, and DAF.

Explore how complement peptides mediate opsonization, inflammation, and immune complex clearance, detailing C3b opsonization, anaphylatoxins, and CR1-mediated removal in spleen and liver.

Explore how immunoglobulin genes are organized in human dna and how germline and somatic mechanisms generate antibody diversity while preserving constant regions and antibody structure.

Showcase how immunoglobulin variable and constant region genes rearrange during B cell differentiation, joining V and C segments to form Ig chains, evidenced by restriction endonuclease digestion and Southern blotting.

Discover how immunoglobulin gene segments organize into light and heavy chains, with V, J, D, and C segments rearranging in germline DNA to create a diverse antibody repertoire.

Examine the organization of lambda and kappa light chain gene segments, including leader peptides, V, J, and C genes, and how rearranged VJ segments form the variable region.

Explore organization of heavy chain genes, including VH, DH, JH, and CH segments, roles in CDR3 and antibody diversity, and how heavy chain rearrangements establish isotype expression without altering specificity.

Describe how V𝜿 and J𝜿 rearrangements form the 𝞙 light chain variable region joined to C𝜿, then transcription, splicing, and translation produce the light chain with a cleaved leader.

Explain how VλJλ rearrangement forms a lambda light chain by joining Vλ with Jλ-Cλ segments, producing a transcript processed into mRNA for translation, with multiple Cλ segments producing four subtypes.

Explore the mechanism of variable region DNA rearrangements in B cells, detailing RSS signals, one- and two-turn spacers, RAG enzymes, Artemis and TdT, and formation of coding and signal joints.

Explain how germline V, D, and J segments rearrange to generate diversity in heavy and light chain variable regions, yielding about 10^8 antigen binding sites.

Explore how junctional flexibility expands antibody diversity beyond VDJ recombination by creating CDR3-driven amino acid variation, while sometimes causing nonproductive rearrangements and B cell apoptosis via stop codons.

Explore how P-addition contributes to antibody diversity by generating palindromic nucleotides at VJ coding joints during recombination, driven by RAG-1/RAG-2 mediated hairpin cleavage.

N-addition generates antibody diversity in the heavy chain cdr3 region via P and N nucleotide additions at the DHJH and VHDJH joints during VDJ recombination.

Explore somatic hypermutation, where mutations in rearranged VDJ/VJ genes increase antibody affinity via CDR changes. Learn how high-affinity B cells are selected and memory B cells form for stronger responses.

Describe antibody class switching, where B cells rearrange heavy-chain constant regions to switch from IgM to IgG, IgA, or IgE, preserving antigen specificity while IgM and IgD coexpress.

Class switching uses switch regions (Sμ, Sγ2) with AID and switch recombinase to excise regions and recombine, changing constant regions (μ to γ2 or α1) while keeping the variable region.

Explore membrane bound immunoglobulins and B cell receptors, detailing how mIg plus Ig-α/Ig-β transmit antigen signals to activate B cells and produce secreted antibodies (sIg).