Basophils and mast cells and
their importance in immune
responses
Mast cells
 Mucosal mast cells - in the mucous
membranes of respiratory and gastrointestinal
tract, produce histamine, serotonin, heparin,
tryptase, leukotriene C4 ..., participate
in parasitosis and allergy
 Connective tissue mast cells - the connective
tissue, producing tryptase, chymase,
prostaglandinD2 ..., are multiplicated in fibrosis,
in parasitosis and allergy are not participating
Mast cell functions
 Defense against parasitic infections
 In pathological circumstances, responsible for the
early type of hypersensitivity (immunopathological
reaction typeI)
 Apply during inflammation, in angiogenesis, in
tissue remodeling
Mast cell activation
Mast cells can be stimulated to degranulate by:
 cross-linking of IgE Fc receptors
 by anafylatoxins (C3a, C4a, C5a)
 direct injury, alcohol, some antibiotics
Mast cell activation by cross-linking
of IgE Fc receptors
 Establishing of multivalent antigen (multicellular parasite)
to IgE on highaffinnity Fc receptor for IgE (FcRI)
 Aggregation of several molecules FcRI
 Initiate mast cell degranulation (cytoplasmic granules
mergers with the surface membrane and release their
contents)
 Activation of arachidonic acid metabolism (leukotriene C4,
prostaglandin D2)
 Start of production of cytokines (TNF, TGF, IL-4, 5,6 ...)
Mast cell activation scheme
Secretory products of mast cells
 Cytoplasmatic granules: hydrolytic enzymes,
proteoglycans (heparin, chondroitin sulphate), biogenic
amines (histamine, serotonin)
Histamine causes vasodilation, increased vascular
permeability, erythema, edema, itching, contraction of
bronchial smooth muscle, increases intestinal peristalsis,
increased mucus secretion of mucosal glands in the
respiratory tract and GIT (helps eliminate the parasite)
 Arachidonic acid metabolites (leukotriene C4,
prostaglandin D2)
 Cytokines (TNF, TGF , IL-4, 5,6 ...)
The role of mast cells in development of allergy
Basophils
 Differentiate from myeloid precursor
 Receptor equipment, containing granules, the
mechanisms of stimulation and functions are very similar
to mast cells
 They are responsible for the emergence of anaphylactic
shock
 Basophil activation markers: CD 63, (CD 203)
Immune mechanisms
of inflammation
(Local and systemic reactions)
Inflammation
* Is a summary of physiological responses to breach the
integrity of the organism, leading to protection against
infection of damaged sites, localization of damage and
healing.
Local body's response to inflammation
Manifestations - pain (dolor), fever (calor), redness (rubor), swelling
(tumor)
Inflammation
• The first signals to the development
of inflammatory responses come from mast
cells, phagocytes, and the substances released
from damaged cells and extracellular
components of matter.
Inflammation
Local inflammation
- increased permeability of blood vessels (vasoactive
amines, complement components C3a, C5a, leukotrienes
..., swelling at site of inflammation) → rednes, swelling
- increased expression of adhesion molecules on endothelia
- activation of coagulation, fibrinolytic, kinin and complement
system
- influence of local nerve endings via prostaglandins → pain
- changes in temperature (IL-1, IL-6, TNF, prostaglandins)
Systemic response to inflammation
- leukocytosis
- fever (proinflammatory cytokines TNF, IL-1, IFN ;
stimulate hypothalamic center of thermoregulation)
- mobilization of tissue metabolism
- induction of expression of Hsp (heat-shock-proteins;
function as chaperones)
- production of acute phase proteins (CRP, SAP, C3, C4;
opsonization and complement activation) by liver after
stimulation with cytokines (TNF-α, IL-1, IL-6)
- increased hepatic synthesis of certain serum transport proteins
(ceruloplasmin, transferrin)
- increased synthesis of protease inhibitors ( macroglobulin)
Septic shock - the massive penetration of microorganisms
into the bloodstream (TNF)
Anaphylactic shock - basophil degranulation and complement
activation with allergen (histamine)
Repair of damaged tissue
- elimination of damaged cells with phagocytes
- activation of fibroplastic mechanisms
- activation of angiogenesis
- regeneration and tissue remodeling
Physiological mechanisms
of regulation of the immune
system
Regulation by antigen
 Induce immune responses and extinction
 Affinity maturation of B lymphocytes
 Maintaining immunological memory
 Antigenic competition
 Threshold density of the complex MHC II-gp Ag on APC
Regulation by antibodies
 Antibodies competes with the BCR for antigen (negative
regulator of B lymphocyte stimulating)
 IgG immune complexes bind to the BCR and FcR on B
cells, resulting in blocking activation of B lymphocytes
 Regulation via idiotypic network
Regulation by cytokines and cellular contact
 Interaction APC - T lymphocyte
 Interaction TH1 – macrophages
 Interaction TH2 - B lymphocytes
 Mutual regulation of activity TH1 versus TH2
 Development of leukocyte subpopulations
Negative regulation of effector cells:
 CTLA-4 - T cell inhibitory receptor, binds ligands CD80 and CD86
 Inhibitory receptors of NK cells
 Self-destruction interaction of the apoptotic receptor Fas with
ligand FasL on the surface of activated T lymphocytes
Interaction of APC with T lymphocyte
T cell:
TCR - antigen-specific receptor (signal 1)
CD4 or CD8 - coreceptor (MHCgp binding)
CD 28 - costimulatory receptor (signal 2, binds CD 80, CD 86)
CTLA-4 - inhibitory receptor (binds CD 80, CD 86)
CD-40L
APC:
MHC gp I + antigenic peptide
MHC gp II + antigenic peptide
CD 80, CD 86 - costimulatory ligands
CD 40
Suppression mediated by T lymphocytes
 Mutual negative interaction TH1 and TH2 cytokine-mediated (TH2
lymphocytes produce IL-4 and IL-10 that suppress the immune
response based on TH1 cells)
 Clonal elimination or anergy of T lymphocytes after contact with
antigen on the surface of other cells than APC (lacking
costimulating signals)
 Regulatory T cells (Tr1 CD 4+) help to maintain tolerance to
autoantigens
Factors influencing the outcome of the
immune response
The same antigen can induce an active immune response
or an active state of tolerance, the result of response
depends on many factors:
 State of the immune system
 Properties of antigen
 Dose of antigen
 Route of antigen administration
Cytokines
(Tissue hormones)
Cytokines
 Regulatory proteins and glycoproteins produced by
leukocytes and other cells
 Essential regulators of the immune system
 Apply also outside the immune system (angiogenesis,
tissue regeneration, carcinogenesis, treatment of many
brain functions, embryonic development ...)
 Cytokines - secreted
- membrane (CD 80, CD86, CD40L, FasL ..)
 Pleiotropic effect
 Operates in a cascade
 Cytokine Network
 Cytokine system is redundant
 Effects of cytokines
- autocrine
- paracrine
- endocrine
 Are known as interleukins (exception: TNF, lymphotoxin,
TGF, interferons, CSF and growth factors)
B cells communicate via cytokines with other
inflammatory cells, such as T cells and macrophages
Distribution of cytokines according their
function
 Proinflammatory cytokines (IL-1, IL-6,IL- 8,IL- 12,IL- 18, TNF)
 Antiinflammatory cytokines (IL-1Ra, IL-4, IL-10, TGF)
 Cytokines with the activity of hematopoietic cells growth factor
(IL-2, 3, 4, 5, 6, 7, 9, 11, 14, 15, CSF, SCF, LIF, EPO)
 Cytokines applying in TH2 humoral immunity (IL-4, 5, 9, 13)
 Cytokines applying in the cell-mediated immunity TH1
(IL-2, 12, IFN, GM-CSF, lymphotoxin)
 Cytokines with anti-virus effect (IFN-, IFN- , IFN- )
Overview of the most important cytokines
Cytokine Produced
Function
IL-1
MF, N
T cell costimulation, induction of TNF and IL-8, pyrogen
IL-2
Th1
Growth factor for T cells
IL-4
Th2, basophils
Th2 differentiation, B cell stimulation, isotype switching to IgE and IgG4, Th1
inhibition
IL-5
Th2, eosinophils
B cell stimulation, growth factor for eosinophils
IL-6
Th2, MF, N
T and B cell stimulation, stimulation of Ig production, induction of acute phase
proteins synthesis, pyrogen
IL-8
MF, other cells
Granulocyte activation and chemotaxis (primarily neutrophils)
IL-10
Th2,M, Treg
Th1 and MF inhibition, B cell differentiation to plasma cell
IL-12
MF, DC, B
Th1 differentiation, NK stimulation
TNF
M, MF, NK
Induction of local inflammation, endothelium activation, induction of apoptosis
TGF
T, MF, platelets
The anti-inflammatory effect (control of lymphocyte proliferation, control of Ig
production, control MF activity), stimulation of fibroblasts and osteoblasts,
gain production of extracellular matrix
IFN
L, M, MF
Inhibition of viral replication
IFN
Fibroblasts,
epithelial cells
Inhibition of viral replication
IFN
Th1, NK
MF activation, stimulation of MHC gp. expression, Th2 inhibition
MF – macrophages; M – monocytes; N – neutrophils; DC – dendritic cells; NK – natural killers; L – lymphocytes; B – B cell; T – T cell
Cytokine receptors
 Consisting of 2 or 3 subunits
 One subunit binds cytokine, other are associated with
cytoplasmic signaling molecules (protein kinases)
 Signaling subunit is shared by several different cytokine
receptors - called receptor family
 Signaling through these receptors may lead to
proliferation, differentiation, activation of effector
mechanisms or blocking the cell cycle and induction of
apoptosis
HLA system
(MHC glycoproteins)
MHC glycoproteins class I
(Major histocompatibility complex)
 The function of MHCgpI is presentation of peptide
fragments from inside the cell (which are produced by
cell, including viral peptides if are present) on the cell
surface to T lymphocytes (cytotoxic CD8+)
 Present on all nuclear cells of the organism
 3 isotypes of classical human MHC gp. (HLA - A,-B,-C)
 3 isotypes of nonclassical MHC gp. (HLA - E,-F,-G;
molecule CD1)
Structure of MHC gp I
 MHC gp class I consists of transmembrane
chain  and non-covalently associated
2mikroglobulin
  chain has 3 domains, 2 N-terminal (1, 2 - binding
site for peptides) and 1 C-terminal domain (3 anchored in the cytoplasmic membrane, a structure
similar to imunoglobulin domain)
 Binding of peptide is necessary for a stable conformation
of MHCgp and thus ensure its long presentation on the
cell surface
Peptides binding to MHCgpI
 MHC gp I bind peptides with a length of 8 to 10
aminoacides
 Certain MHC gp molecule binds peptides sharing
common structural features - coupling motif (critical are
aminoacides near the end of peptide)
 The binding of endogenous peptides occurs in the
endoplasmic reticulum during biosynthesis of MHC gp
Peptides binding to MHCgpI
 After a string  and 2mikroglobulin create in the ER,
folding into the correct conformation and the mutual
association and the association of an appropriate
peptide, the complex is further processed in the Golgi
apparatus and then is presented on the cell surface
 Linked peptides derived from proteins degraded
proteasome, which cleaves cytoplasmic proteins for
destruction (labeled with ubiquitin), peptide fragments
are transported into the ER by specific membrane pump
Peptides binding to MHC gp I
Non-classical MHC gp I
 HLA - E,-F,-G; CD1 molecules
 Structurally similar to classical MHC gp
 Are less polymorphic
 There are only on some cells
 They specialize in binding of specific ligands
 HLA-E and HLA-G - occurs on the trophoblast cells
 Complexes of HLA-E and HLA-G with peptides are
recognized by inhibiting receptors of NK cells and
contribute to the tolerance of the fetus in utero
 CD1 molecules - bind glycolipids (recognized by NK-T
lymphocytes)
MHC glycoproteins class II
 The function of MHC gpII is the presentation of peptide
fragments from protein whitch were engulfed by antigen
presenting cell on the cell surface to T lymphocytes
(auxiliary CD4)
 Occur on the APC (dendritic cells, monocytes,
macrophages, B lymphocytes)
 3 isotypes of MHC gpII (DR, DQ, DP)
Structure of MHC gp II
 MHC gp II consist of 2 non-covalently associated
transmembrane subunits  and 
 The peptide binding site consists of N-terminal
domains 1 and 1
 Binding of peptide is necessary for a stable MHC gp
conformation and thus ensure its long presentation on
the cell surface
Binding of peptides to MHC gp II
 MHC gpII bind peptides with a length of 15 to
35 aminoacides (but possibly longer - because
the peptide binding site is open at both ends)
 Certain MHC gp molecule binds peptides sharing
common structural features - coupling motif
Binding of peptides to MHC gp II
 After a string  and  are created in ER, fold into
the correct conformation and the mutual
associated are connected with another
transmembrane chain called invariant chain,
which blocks the binding site for the peptide,
this complex is further processed in the Golgi
apparatus, secretory vesicles isolated from GA
merge with endosomes, then split the invariant
chain and peptide fragments from cell absorbed
proteins bind into binding site of MHC gp and
the complex is then presented on cell surface
Peptides binding to MHC gp II
HLA system – genetic background
 HLA complex is localized
on chromosome 6
 Codominant inheritance of HLA
( Individual has 3 cell surface isotypes
of HLA molecules (HLA-A,-B,-C) mostly
in 2 different alelic forms )
Polymorphism of MHC glycoproteins
 For MHC gp is typical high polymorphism (except the
non-classical MHC gp)
 Polymorphism has a protective significance at individual
and population level
 Ppolymorphism MHC gp causes complications in
transplantation
Carry out during the testing before transplantation ,
in the diagnosis of certain autoimmune diseases
and in determination of paternity
HLA typing
• Serotyping
• genotyping