Question

Explain the major responsibility of the spleen with regards to the immune surveillance responses, compared to the major responsibilities of the lymph nodes and the mucosal tissues?

Answer 1

we can differentiate the responses of the adaptive immune system into 2 compartments

• 1st compartment comprising the peripheral lymph nodes and spleen

1. this compartment respond to antigens that have entered the tissues or spread into the fluid
2. it is confined in expression
3. lymphocytes work in particular compartment
4. and specifically expressed within the tissues

• 2nd compartment respond to antigens that are located near the surface where most pathogens invade - mucosal immune system.

the major responsibility of the spleen with regards to the immune surveillance responses

• the main filter of blood born diseases
• filter for antigen
• key organ for iron metabolism
• erythrocyte homeostasis
• the site where immune responses that are deleterious to host are regulated
• control antigen tolerance
• host all types phagocytes including macrophages, DCs, monocytes
• splenectomy can selectively respond to high antigen tolerance
• sense apoptotic deaths
• regulate peripheral tolerance by expressing autoimmune regulator gene'
• spleen - 2 types of regions - red pulp

- white pulp

• red pulp - contain macrophages to filter blood and recycle iron

1. trap and remove blood born antigens
2. initiate innate and adaptive immune responses
3. work against pathogen
4. phagocytose aging red blood cells
5. M2 macrophages remove specific blood-borne bacteria and viruses

• white pulp - allow generation of antigen-specific immune respose

1. protect the body against diseases
2. many bacterial, fungicidal and viral infection

major responsibilities of the lymph nodes

• lymphatic vasculature plays an important role in immune modulations
• coordinate antigen transport
• coordinate immune trafficking from peripheral tissues to lymphoid organs
• control of immune cell migration
• used as a route to immune cell trafficking
• lymphocytes encounter foreign antigen and can access the lymphatic capillaries
• maintain homeostasis
• regulate lymph transport
• hostile microenvironment causing inflammation, harmful antigen are removed by draining the excess fluid into lymphatic vessels
• play a role in repairing the damaged tissues
• act as major mediators of pathogen clearance
• inflammation resolution
• closely interact with immune cells for performing specific functions
• participate in immune responses by releasing cytokines and chemokines in response to environmental change

major responsibilities of the mucosal tissues

• mucosal surface is the primary point of contact for numerous infectious agents
• defend organism from infections
• discriminate between foreign particles and pathogens
• prevent harmful responses from innocuous agents
• initial defense occurs through - mucus, cilia, epithelial cells etc
• specialized action was taken by - surveilling myeloid phagocytes
• induction and coordination of adaptive immune response at the mucosal surface
• DC act as a surveillance system to sense infection in mucosal tissues
• function as an antigen presenting cell to a difference between T and B cells
• mucosal tissues contain lymphatic cells which sense invading the foreign organism
• T-cells attack and clear pathogen
• B cells secrete IgA
• these cells contribute to host defense