Immunology- Chapter 10.1-10.3 B cells

Humoral Immunity

Immunity concerning the humoral system- proteins circulating in the blood such as antibodies (adaptive) or complement (innate)

Thymus Dependent antigens (TD)

antigens that elicit antibody production with the involvement of T cells

Thymus Independent antigens (TI)

antigens that elicit antibody production without the involvement of T cells

CD40 Ligand

receptor for CD40 on activated CD4 T cell, is a co-stimulatory molecule. 

IL-21

cytokine produced by T cells that activates STAT 3 in B cell, and promotes survival/proliferation of B cells 

BC Co-Receptor Complex

transmembrane signaling receptor on BC surface that binds to complement fragments on bacterial antigens (CD-19, 81, 21) 

CR2

CD21, complement receptor that is a part of the BC co-receptor complex

Linked Recognition

the initial step of antibody production. CD4 TC and BC recognize the same antigen, but different epitopes, leads to TC mediated activation of the BC 

Hapten Carrier Effect

when antibodies are produced against small (non pathogenic) chemical group called a hapten, by attaching a protein to it

S1PR1

sphingosine 1 phosphate receptor 1, is a G protein coupled receptor activated by sphingosine 1 phosphate

TC Areas

zones in lymphoid organs that are enriched with naive TCs

Primary Lymphoid Follicles

area where resting naive BCs are located in a peripheral lymphoid organ

Subcapsual Sinus (SCS)

site of lymphatic entry in lymph nodes lined with phagocytes (macs) which capture opsonized antigens from draining tissue

Marginal Sinus

In the spleen. blood filled vascular network that branches from central arteriole and demarcates each area of white pulp 

Plasmablasts

BC in lymph node that shows features of plasma cells

Germinal Centers

sites of intense BC proliferation/differentiation that develops in lymphoid follicles during an adaptive immune response (somatic hypermutation and class switching) 

Mantle Zone

router ring of B lymphocytes that surround lymphoid follicles

Light Zone

region of germinal center that is enriched with BC interacting with Tfh cells and antigens on FDCs

Dark Zones

in germinal centers, region enriched with rapidly dividing activated BCs 

Somatic Hypermutation

mutations in the V region of DNA of rearrangement genes that produce variant immunoglobulins 

Affinity Maturation

increase in affinity of antibodies for their specific antigen as adaptive progress

Centroblasts

large, rapidly dividing activated BCs in the dark zone of the germinal center.  

• express CXCR4 and CXCR5 receptors 

• Stromal cells in the dark zone produce CXCL12 which is a ligand for CXCR4, to retain the centroblasts

Centrocytes

small BCs that derive from centroblasts.

• Occur once a centroblast stops proliferating and stops expressing CXCR4 

• Populate the light zone

AID 

activation induced cytokine deaminase, an enzyme that initiates hypersomatic mutation

Tingible Body Macrophages

macrophages engulfing apoptosis BCs

Cyclic re-entry model

(BC behavior) activated BCs in the germinal center lose and gain expression of chemo-kine receptor s CXCR4 when they move from light zone to dark zone and back again, under CXCL12 

APOBEC1

apolipoprotein B mRNA editing catalytic polypeptide, an RNA editing enzyme that deaminase cytidine to uracil in mRNAs

Mismatch Repair

DNA repair that causes mutations like somatic hypermutation in BCs

Base Excision Repair

DNA repair that causes mutation is involved in somatic hypermutation in BCs 

Uracil DNA Glycolase

enzyme that removes uracil from DNA in a repair pathway that leads to somatic hypermutation, class switching, and gene connection

Error Prone DNA Polymerase

DNA polymerase operates during DNA repair (repair basic lesions)

Isotype Class Switching

a somatic gene recombination process in activated BCs that repairs on heavy chain constant region with one of a different isotype (starts as IgM then switches to IgG, IgA, and IgE)

Switch Regions

genomic regions located between JH and heavy chain

Polymerase Stalling

halting of the RNA polymerase during transcription of a gene at locations within a gene locus (isotype class switching)

R Loops

structures formed when transcribed RNA displayed the non-template strand of the DNA double helix, at switched regions in the immunoglobulin constant region (promotes class switch recombination) 

RNA Exosome

multi-subunit complex with processing and editing RNA 

G-Quadruplix

structure formed from G rich regions of DNA

Memory BCs

B and T lymphocytes that mediate immunological memory

BC Mitogens

any substance that non specifically causes BCs to proliferate

Capsulate Bacteria

Bacteria surrounded by a polysaccharide shell that resists in phagocytes (results in pus, pyogenic bacteria)

Canonical NFkB Pathway

involves IKK

Non Canonical NFkB Pathway

no IKK, involves NIK instead