Self/nonself discrimination

Mon Jul 18 15:43:29 EST 1994

Frauwirth (BioKen)) says:
>Although antigen presenting cells (APC's) are made more effective by
>opsonization and Ab/Fc-receptor interactions (or, in the case of B cells,
>binding of antigen to speicific cell-surface receptors), they are perfectly
>capable of presenting "random", soluble proteins, including serum proteins.
>We use the B cell hybridoma LK35.2 as an APC in our lab, and it is quite
>competent at presenting ovalbumin and hen-egg lysozyme to T cells.

        If you surround ANY cell with a high enough amount of a protein, some
may get inside and find its way to a compartment where it may end up being
presented as antigen fragments in association with MHC. Are your LK35.2 cells
maintained in serum-free medium? If not, how do you know that some antibodies
are not present? Anyway, it would be appropriate to question whether uptake in
the absence of antibodies is really physiologically relevent. Biological
systems have natural antibodies, albeit of low specificity, which have been
screened to eliminate anti-self antibodies, and thus should be relatively
specific against non-self antigens.

>In the absence of specific antibodies (as is likely to be the case early
>in an immune response to a "new" antigen), APC's can pick up proteins using
>pinocytosis.  Apparently dendritic cells (in the thymus) are particulary
>good at this.

         As indicated above, I doubt tha absence of sufficiently specific
                              Sincerely, Don Forsdyke, Discussion Leader.

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