1. Dendritic cells are antigen-presenting cells that can be divided into several types based on location, including Langerhans cells in the skin, interstitial dendritic cells in tissues, and circulating dendritic cells in blood and lymph nodes. 2. Dendritic cells are the most efficient antigen-presenting cells as they constitutively express high levels of MHC class II and co-stimulatory molecules. They take up, process, and present antigens to activate T helper cells. 3. Langerhans cells in the skin take up antigens and migrate to lymph nodes to activate T cells. Interstitial dendritic cells are found in tissues and play a role in immune responses

1. 1. Lymphoid cells T cells 4. Mast cells
B cells
NK cells (Null
cells)
2. Mononuclear
cells
Monocytes 5. Dendritic
cells
Langerhans cells
Interstitial DC
Macrophages Interdigitating DC
Circulating DC
3. Granulocytic cells Neutrophils
Eosinophil
Basophil
Cells of the immune system

2. DENDRITIC CELLS
-It resemble the dendrites of nerve cells (dedrites- small projections from
nerve cells)
-Hence called as dendritic cells

3. Formation of dendritic cells
1. Through lymphoid lineage
2. Through myeloid lineage

4. • Dendritic cell- most efficient antigen presenting cell
- express Class II MHC
-express B7 co-stimulatory molecules
• Other APC- B cells and Macrophages
express Class II and B7, only when activated by Ag
• Dendritic cells
Express Class II and B7- always
So, more efficient APC than B cells and macrophages

5. Function of dendritic cells
• acts as APC
•Takes up Ag by phagocytosis
Processes it
Presents Ag with Class II MHC to TH cell

6. All dendritic cells
share the ability to
 pick up and process Ag molecules, and
 to migrate centrally to the lymphoid organs, where T cell interaction occurs.
5. Dendritic
cells
Langerhans cells
Interstitial DC
Interdigitating DC
Circulating DC-
Veiled cell, Blood DC
Dendritic
cells
Ag with CII
MHC TH

7. Langerhans cells
 Discovered by Paul Langerhans in 1868 in the epidermis
 Is the specific type of dendritic cells present in the skin. Also present in
mucosa, and lymphoid tissues
Function of langerhans cells
 When skin is infected with pathogens, LC become a fully functional APC by taking
up the antigen and processing it
 Skin is an important barrier to infection and it has been generally assumed that
the Langerhans cells only serve to warn the immune system of skin pathogens.
 During the initiation of an immune response, epidermal LC migrate from the skin
to draining lymph nodes to present processed antigens to T cells and induce
antigen-specific T cell immunity
Blood (veiled cells) Lymphoid system
Langerhans
cells
Ag
Ag with CII
MHC
Langerhans
cells
Ag with CII
MHC TH
Skin

8. Interstitial/dermal DC
 interstitial/dermal DC are also present in skin
 play an important role in the regulation of skin immune responses
 LC and IDC bear FcgR, hence can bind to Ag-Ab complex eg., they are
involved in the capture and the degradation of HIV-1 IgG immune
complexes
 IDC were first identified in the interstitium of non-lymphoid organs
(interstitium-the space between cells in a tissue)
Langerhans cells
Interstitial DC
Interdigitating DC
Circulating DC- Veiled cell, Blood DC
LC and IDC FcgR Ag-Ab complex

9.  Studies have shown that the interstitia of most organs, except the brain,
contain interstitial DC
Problem in organ transplantation
 The IDC are normally present within organ allografts
 These cells present in the donor are eradicated by the Host
 It contributes substantially to graft immunogenicity
 To prevent it, the IDC present in the donor organ are eradicated to
improve organ graft survival
Donor
IDC
Host

10. Interdigitating DC
 Interdigitating DC , exhibit a low antigenic processing
activity, but express a high density of MHC class II and T
cell stimulatory molecules
Interdigitating
DC
CII
MHC
TH Cell
LC and IDC FcgR Ag-Ab complex
 lack of FcR and CR (complement receptor), which are
present in other DC like Langerhans cell and Interstitial DC

11. Veiled Cells
Langerhans cells in skin undergone antigen uptake and processing
When they move to the lymphatic system through blood, they are called as veiled
cells
Blood (veiled cells) Lymphoid system
Blood DC
 Peripheral blood DC were isolated by Van Voorhis et in 1982.
 They showed that 0.1% to 0.5% of human peripheral blood mononuclear
cells and had the same cytological features as rodent DC.
 Both groups of DC (veiled cells and blood DC) may be involved in antigen
transfer to the T cells of the lymphoid system
Langerhans
cells
Ag
Ag with CII
MHC
Langerhans
cells
Ag with CII
MHC TH
Skin
Circulating DC

12. Another type of dendritic cell
Not derived from bone marrow – is follicular dendritic cell
follicular dendritic cell
1. Do not express Class II MHC
2. So- is not an APC
3. Cannot activate TH
4. Exclusively present in lymphoid follicles of lymph nodes
5. Consists of R for Ab
6. So, can bind with Ag- bound to Ab (Ag-Ab complex)
FD R for Ab
Ag-Ab
complex

13. FDC
B cell
Folicular DC（FDC）
 Present in follicle of
Lymph Node
 no expression of class
Ⅱ MHC
 high level of FcR and
C3bR.
Follicular
dendritic cell
FcR Ab-Ag complex
Activates surrounding B cells in lymph node
Interacts with