splenic extravasation

[Ralph A. Sorensen]

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>From: cschmidt at vub.ac.be (Schmidt Corina)
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>To: rsorense at gettysburg.edu (Ralph A. Sorensen)
>Subject: Re: splenic extravasation
>Newsgroups: bionet.immunology
>Organization: Brussels Free Universities (VUB/ULB), Belgium
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>In article <9502161255.AA23618 at popserver.jr.cc.gettysburg.edu> you wrote:
>: In preparing a lecture on the functional anatomy of lymphoid tissues, I have 
>: encountered a question that leaves a hole in my notes: how does 
>: extravasation of lymphocytes occur in the spleen? All of my sources wax 
>: eloquent on the role of the HEV in lymph nodes and unencapsulated lymphoid 
>: tissue, but the only reference I find to the spleen is that there is no HEV! 
>: To further my confusion, while it is no problem for lymph node lymphocytes 
>: to return to the circulation via the efferent lymphatics, how do splenic 
>: lymphocytes return from the white pulp? Could someone help me out and/or 
>: point me to a reference? Thanks.
>:                                                     
>: Ralph A. Sorensen
>: Biology Department, Gettysburg College
>: Gettysburg, PA 17325           
>: rsorense at gettysburg.edu             
>: 717-337-6168 (voice)  717-337-6157 (fax)       
>:
>
>I am working on metastasis of malignant lymphoid cells to the spleen and
>therefore also very interested in the invasive behaviour of normal lymphocytes
>in the spleen. As far as I know there is indeed little known about the 
regulation
>of splenic extra- and intravasation. 
>There exists an interesting review about the structure and physiology of 
lymphatic tissues, whrere also the spleen is nicely described.
>ref.: Structure and Physiology of Lymphatic Tissues, Anderson A.O. and Anderson
>N.D. in: "Cell Function in Immunity and Inflammation" Oppenheim J.J.,
>Rosenstreich DL, Potter M. Eds., Elsevier Amsterdam 1981.
>In case it is difficult for you to have acces to this book, I cite you
>the important part about spleen emigration:
>
>"lymphocyte traffic through the splenic red and white pulp is noT regulated by 
>the same mechanisms that determine lymphocyte homing into the lymph nodes.
>Many of the lymphocytes entering the spleen in the arterial blood bypass the
>white pulp and flow along with other blood elements into the reticulum of 
the red pulp cords and sinuses to exit via the splenic vein. These cells 
would be returned to the blood within 2 to 3 hours after enetering the 
spleen. However, some
>arterioles terminate in sinuses adjacent to the white pulp, others empty 
>directly into the marginal zone. Cells entering here may remain in the spleen
>for upto 12 hours. After variable periods of residence here, some recirculating
>cells exit through the efferent lymphatics, while others appear to move back
>out via bridging zones into the red pulp sinuses. The magnitude of lymphocyte
>recirculation via splenic efferent lymph or venous return remains to be
>determined....".
>
>So, there do exist efferent lymphatics in the spleen (but no afferent 
lymphatics!). Furthermore,  arterioles seem to terminate in sinuses, so 
lymphocytes do not
>need to transmigrate endothelial layers to enter the spleen.
>The retention of lymphocytes in the spleen may be regulated via their
>interaction with macrophages in the marginal zone, ref.:Sialoadhesin on
>macrophages, its identification as a lymphocyte adhesion molecule 
>van den Berg T et al., J.Exp.Med. 176, 647-55, 1992.
>
>I hope this infomation can be of some help for you.
>
>Greetings,
>
>Corina Schmidt
>dep. Cellular Immunology
>Free University Brussels
>Belgium             
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Ralph A. Sorensen
Biology Department, Gettysburg College
Gettysburg, PA 17325           
rsorense at gettysburg.edu             
717-337-6168 (voice)  717-337-6157 (fax)       
            
        
                                                        
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