T A B L E
3 5 - 1
Components of the Immune System (continued)
Cellular (Leukocyte)
Components
Principal Functions
Characteristic
Receptors/Specific APC
Recognition
Related
Figure(s) or
Tables
Myeloid Cells
Neutrophils
First cells recruited to sites of
Adhere to foreign cells via
Figure 4
Mature in bone marrow
inflammation, dominant
phagocytic granulocyte, able to
mediate ADCC (antibody-
dependent cell-mediated
cytotoxicity), major defense
against pyogenic bacteria, use
respiratory burst to kill cells
CDllb/CD18
No MHC proteins. Neutrophils
are attracted to sites of
complement activation by C5a,
a chemotactic peptide from C5
Basophils
Blood “analog” of tissue mast
cell, stimulated by comple-
ment C3
Possess Fc receptors that bind
IgE causing degranulation and
histamine release
Mast cells
Tissue granulocytes that
Fc receptors that bind IgE
Mature in bone marrow,
produce cytokines,
causing degranulation and
resident in tissue
release heparin, histamine
histamine release
Eosinophil
Attack parasites too large for
phagocytosis, possess granules
that contain toxic proteins,
adhere to foreign organisms via
C3b. Release protins and
enzymes that damage foreign
organism membranes, kill with
active oxygen burst. Engage in
IgE-mediated ADCC
High-affinity receptors for IgE,
bind via Fc region of antibody
Monocytes
Mononuclear phagocyte in
Express MHC Class II surface
Figure 2
Mature in bone marrow,
blood, are precursors to tissue
proteins, do not possess
found in blood
macrophage. Process protein
antigens and present peptides to
T-cells via MHCI and II. Engage
in IgG-mediated ADCC
antigen-specific receptors
Macrophages
Tissue phagocytes (APCs) that
Express MHC Class II surface
Figure 2
Mature in bone marrow
processes antigens for
proteins, do not possess
as monocytes,
presentation to T cells, possess
antigen-specific receptors, but
monocytes mature
further to tissue
resident macrophages
MHC receptors, principal attack
is on bacteria, viruses and
protozoa that enter cells.
Engage in IGG-mediated ADCC
have receptors for C3b.
Dendritic cells
Follicular
Antigen-antibody and Ag-Ab
complexes with complement
are localized in these cells.
Involved in maintenance of B
cell memory
Possess
Fc receptors
No MHC class II receptors
Interdigitating
Found in skin (Langerhans
cells) in T cell areas of lymph
nodes and spleen. Recognize
and endocytose foreign carbo-
hydrate antigens that are not
found in vertebrate animals. Act
as APCs to CD 28-bearing T cells,
stimulated by IFN
a ,
TNF
a.
Do not have Fc receptors
Possess
MHC class II receptors.
Express
CD80
and
CD
86
(continued)
