Thanks for your thoughts, Tim.
I've found this article about MHC (part of it is below the page).
My initial ideea was that, the B cells, as seen below,
would be sort of unable to reach the viruses due to the
already damaged paths they usually require to follow, in order to get
to a
point in our body. It's like a polar bear that would try to get to a
group of seals, from a kilometer apart, when the ice would have breaken
in the middle.
By the time the polar bear gets to the remaining seals by swimming
through the
water, some of the seals are hiding somewhere else.

Can actually the B cells penetrate any part of the skin/mucosa even
when it has been badly affected by the viruses?
There are viruses localized behind those damaged areas that
would continue their job due to this very reason: the B cells cannot
reach them before the skin continues to get to a point where the damage
caused by the scars and such, will become hard to heal (as 10 days as
usually it requires without the help of antivirals).

It sounds like a race between the B cells and the viruses. The faster
the B cells get to them, the better for the skin.

Of course, all these speculations are on a very presumptive level.
I think that would be of interest to know.

Perl von Molson

Molecular biology of MHC proteins

The classical Mhc molecules (also referred to as HLA molecules in
humans) have a vital role in the complex immunological dialog that must
occur between T cells and other cells of the body. At maturity, Mhc
molecules are anchored in the cell membrane, where they display short
polypeptides to T cells, via the T cell receptors (TCRs). The
polypeptides may be "self," that is, originating from a protein created
by the organism itself, or they may be foreign, originating from
bacteria, viruses, pollen, etc. The overarching design of the MHC-TCR
interaction is that T cells should ignore self peptides while reacting
appropriately to the foreign peptides. Foreign peptides that provoke an
immune response are termed antigens.

Interestingly, the immune system has another, equally important method
to identify antigen: B cells with their membrane-bound antibodies, also
known as B cell receptors (BCRs). However, while the BCRs of B cells
can bind to antigens without much outside help, the TCRs of T cells
require "presentation" of the antigen: this is the job of Mhc. It is
important to realize that the vast majority of the time, Mhc are kept
busy presenting self-peptides, which the T cells should appropriately
ignore. A full-force immune response usually requires the activation of
B cells via BCRs and T cells via the Mhc-TCR interaction. This
duplicity creates a system of "checks and balances" and underscores the
immune system's potential for running amok and causing harm to the body
(see autoimmune disorders.)

All Mhc molecules receive polypeptides from inside the cells they are
part of and display them on the cell's exterior surface for recognition
by T cells. However, there are major differences between MHC class I
and II in the method and outcome of peptide presentation.

   * Mhc Class I molecules are found on almost every nucleated cell of
the body. Class I molecules are heterodimers, consisting of a single
transmembrane polypeptide chain (the a-chain) and a ß2 microglobulin
(which is encoded elsewhere, not in the MHC). The a chain has two
polymorphic domains, a1, a2, which present peptides derived from
cytosolic proteins to the immune system. The peptides are short,
consisting of 8-10 amino acid residues.

Because class I Mhc is loaded with proteins found in the cytosol, it is
the primary way for a virus-infected cell to signal to T cells. It
interacts exclusively with CD8+ T cells (also known as cytotoxic T cell
lymphocytes or CTLs). The fate of a virus-infected cell is almost
always apoptosis, or programmed cell death, initiated by the CD8+ T
cell. This response seems like "killing the messenger," but the
messenger in this case is virally infected and probably represents a
risk of contagion for neighboring cells.

   * Mhc Class II molecules are found only on a few specialized cell
types, including macrophages, dendritic cells, activated T cells, and B
cells, which may be referred to collectively as "antigen-presenting
cells" (APCs). Class II molecules are also heterodimers, but in this
case consist of two homologous peptides, an a and ß chain, both of
which are encoded in the MHC. The peptides presented by class II
molecules are derived from extracellular proteins (not cytosolic as in
class I). Loading of class II molecules must still occur inside the
cell; extracellular proteins are endocytosed, digested in lysosomes,
and bound by the class II MHC molecule prior to the molecule's
migration to the plasma membrane. The peptides are longer, generally
between 15-24 amino-acid residues.

Because class II Mhc is loaded with extracellular proteins, it is
mainly concerned with presentation of extracellular pathogens (for
example, bacteria that might be infecting a wound or the blood.) Class
II molecules interact exclusively with CD4+ T cells (also known as
helper T cell lymphocytes or HTLs). The helper T cells then help to
trigger an appropriate immune response which may include localized
inflammation and swelling due to recruitment of phagocytes or may lead
to a full-force antibody immune response due to activation of B cells.

http://en.wikipedia.org/wiki/Major_histocompatibility_complex