26 Feb 2016

Immune system 'patrolling' cells further understood

By Dr Jodie Abramovitch

Within the immune system there are patrolling cells that are constantly scanning the body for signs of infection. They are known as antigen presenting cells. Dendritic cells (DC) are the most efficient example of an antigen presenting cell. When DC find an infection, they are able to alert other cells of the immune system to attack and destroy the infection. Therefore the functions of DC are really important in an effective immune response.

Associate Professor Mark Wright, Head of
the Leucocyte Membrane Protein Group
and senior author of this study
Tetraspanins are a type of protein that are found at the cell surface. Here they bind and bring together (“organise”) other proteins and receptors at the cell surface. CD37 and CD82 are tetraspanins that allow DC to communicate with other immune cells that there is an infection present. CD37 is important for movement of DC to lymph nodes where they find other immune cells. The role of CD82 in DC migration is unclear.

In a recent study published by the Leucocyte Membrane Protein laboratory from the Department of Immunology and Pathology, in collaboration with Melbourne University and international colleagues, the roles of CD37 and CD82 in co-ordinating DC function in response to infection was assessed.

By studying activated DC, it was found that CD82 appeared to have an opposing function to CD37. Whereas CD37 expression was down-regulated following activation of DC, CD82 was up-regulated and restrained DC migration to lymph nodes. DC that were deficient in either CD37 or CD82 were unable to become fully functional and DC that were deficient in CD82 were able to spread much further than CD37 deficient DC. Thus, unactivated DC were observed to have high CD37 expression and low CD82 expression leading to a highly mobile cell that is able to travel easily around the body. Activated DC (DC that have sensed an infection) have low CD37 expression and high CD82 expression which limits mobility of the DC but is able to efficiently signal to immune cells that an infection is present.

This study has detailed a biology of DC that was not previously known and highlights the importance of tetraspanins in coordinating DC function. 

Reference: Jones ELWee JLDemaria MCBlakeley JHo PKVega-Ramos JVilladangos JAvan Spriel ABHickey MJHämmerling GJWright MDDendritic Cell Migration and Antigen Presentation Are Coordinated by the Opposing Functions of the Tetraspanins CD82 and CD37. J Immunol. 2016 Feb: 196; 978-87. 
doi: 10.4049/jimmunol.1500357

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