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autoimmune dz continued. 

mechanisms of autimmune tissue damage:

antibodies & complement	- C-activation ==>inflammation, lysis. eg true 
AIHA, etc

Ag/Ab complexes - C Fixation ==>tissue damage ==> interference with organ 
fx. occurs when you have Ab against particular epitope. the neutrophil is 
main cell type causing the tissue damage -- neut infiltration, releaseof 
enzymes, etc.

Tc and Th cell activation: Tc==>lysis of target tissue, Th==>lymphokine 
release, tissue damage. in order to get Tc activation and lysis by 
perforins, you need Th cells. mostly Th1 cells, to give IFNg and IL2 to 
cause proliferation of Tc cells. so from a stimulating standpoint, the 
self Ag must trigger Th and Tc cells, so must be presentation of part of 
Ag by MHCI and part by MHCII.

macrophage- activated by lymphokines - may become cytotoxic. when 
activated by IFNg become very active, toxic, produce toxic stuff, and 
cause tissue damage. armed w/cytophilic Ab via Fc may attack target cell.


NK cells 

K cells- any WBC w/an Fc receptor that can crosslink Ab against target 
and cause ADCC.

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see fig 4.1 in handout - thyroid follicle..Th cells trigger B cells, make 
Ab against target cell. Ab binds epitope, then effector cells eg mphage, 
K, etc can bind Ab and attack target cell, and Tc cell can bind epitope 
in conj w/MHCI and attack by direct contact via perforins. Plasma cells 
will make a lot of Ab and with lot of Ab and complement you could get 
lysis but that is less frequent than the cell mediated mechanisms.

some prototypes of autoimmune dz:
is seen in animals but we don't have as much info about their 
histocompatibility Ag, genetics, etc, while it is well worked out in 
humans. seems rarer in animals. anyway, two main categories:

organ specific, where attack is directed against one particular organ, eg 
thyroid: hashimoto's thyroiditis (t cell mediated), thyrotoxicosis (don't 
see death of thyroid, see excess stimulation by Ab resembling TSH 
attaching and fooling the receptor. so this autoimmune dz causes no 
tissue destruction, but causes overstimulation. stomach: pernicious 
anemia, caused by Ab against a protein necessary for vitamin B12 to be 
absorbed, so patients can't absorb B12 and get anemic. adrenal: addison's 
dz - cortex destroyed, lose gluco and mineralocorticoids. pancreas: IDDM 
- islet cells destroyed. treatment of these organ specific diseases is 
not by manipulating the immune response, but by providing whatever it is 
that immune system is destroying: eg thyroid, insulin, B12, steroids, 
etc. so tx = metabolic compensation.

in contrast, other dz are systemic autoimmune dz. they mostly cause an 
attack against more than one tissue component. you have more widespread 
problems.

muscle - dermatomyositis - muscle and CT attacked
Systemic lupus erythematosis: SLE
rheumatoid arthritis
scleroderma

in these systemic dz, you try to manipulate the immune response, eg 
downregulate the attack against the tissues. 

so there are organ specific autoantibodies, and systemic ones (non organ 
systemic).  thyroid autoAb overlap with stomach Ab, so hashimoto's 
thyroiditis and pernicious anemia often occur together, but there is 
little overlap with non-specific autoAb. 

organ specific dz: Ag localized to given organ, Ag in organ is target or 
immunological attack (eg in thyroid could be autoAg on surface of the 
cells or actually a cytoplasmic component of thyroid cells, and there is 
overlap w/other organ specific ab and dz.

non organ specific: Ag is widespread throughout body. we see Ag/Ab 
complexes depositing all over esp in kidneys, joints, and skin. SLE- lots 
of deposition in glomeruli. can be overlap with other non organ specific 
ab, but i think that's kinda rare. he didn't go over it.

autoimmune dz manifestations:

BLOOD: anemia, leukopenia, thrombocytopenia
CNS: allergic encephalitis, demyelinating dz
endocrine: thyroiditis, hypoparathyroidism, diabetes, addison's
GI: pernicious anemia, ulcerative colitis, regional ileitis, gluten 
sensitive enteropathy.

Systemic DZ

SLE: underlying problem is that you make Ab against your own DNA and 
nuclear protein. single or double stranded DNA. when you start getting 
the appearance of Ab against DNA, you get immune complexes which localize 
ina  secondary fashion in kidney, joints, bv, etc. so immune complex dz 
is not the problem, per se, it's a reaction caused by the problem. how do 
you get triggered by your own DNA? DNA is always int he cells, how can it 
combine w/Ab? think of GI, LN, BM - lots of cells undergoing apoptosis. 
so lots of DNA gets phagocytosed, so it's exposed to immune system. most 
don't make Ab to DNA because it's genetically determined. if predisposed 
genetically to autoimmune dz, will make the Ab. also, in SLE, the patient 
is also prone to making Ab to other tissue components like RBCs, thyroid 
tissue, platelets, etc. so these patients have this tendency to make 
these other autoAb, which could cause separate problems. 
realize the anemia isn't due to antiDNA Ab, it's due to other anti RBC 
Ab. ditto w/thrombocytes. 

rheumatoid arthritis: 

organ specific:
no organ is exempt. any organ can be involved. 

an exampleof a particular organ specific dz in expt'l animal. CHICKENS - 
normal chicken and "obese" chicken. obese chickens get spontaneous 
thyroiditis and weird fat deposits, silky feathers, hypothermia, act like 
people w/hashimoto's. histology of their thyroid has major mononuclear 
infiltrate complete w/germinal center. so people thought this is a cell 
mediated phenomenon and tried to see if T or B cell mediated - but in 
birds, thymus and bursa can be separately eliminated, so...and 
thymectomized birds had WORSE thyroiditis than bursectomized birds. so 
probably B cell mediated disease, since is better when bursa is removed. 
but wait! disease gets WORSE than control when thymus is removed. so, T 
cells must be playing some role as well. possibly with the thymectomy, 
you are removing a category of T cells like "suppressor" cells or 
somethign...some T cells w/suppressor activity must normally be present 
preventing dz from being worse than it regularly is. when you look at 
where autoAb located, it's usually at apical part of the acinar 
structure, but in other conditions could also be directed against nuclear 
DNA proteins, and that means that not only one component of thyroid cell 
can be self epitope, but a variety can do that, causing autoimmune dz.

is it necessary to have MHCII expression in organ being attacked by self 
Ab? normally in thyroid acinar structure, only a dendritic cell would 
have MHCII, not any actually thyroid cells. of course thyroid cells would 
express class I, though. So, normally, you oculdn't activate Th cells 
because there's no MHCII. but when autoimmune thyroiditis occurs, thyroid 
cells start expressing MHC II on their surfaces and can present self 
epitopes all of a sudden. that occurs primarily through the intervention 
and liberation of IFNg. IFNg is one of main triggers activating tissues 
to start expressing MHCII. keep that in mind - important potential 
mechanism for induction of autoimmune dz. 

so any inadvertant inflammatory rxn in thyroid, even neck trauma, if you 
build up a small nidus of infl. w/t cells making IFNg, if person 
predisposed to react to self epitopes, this could induce autoimmune 
thyroiditis.  

thyrotoxicosis: production of Ab against receptor normally bound by TSH. 
thyroid fooled , so overproduces thyroid hormones. these patients have 
increased hunger, can't gain wt, increased metabolism, etc. treatment: 
radioactive iodine - kill part of thyroid. or steroids - cut down immune 
response to TSH receptor.

so is there an association w/MHC gene products and autoimmune dz?

IDDM - if you express DR3 and DR4 of MHC II, you have a 20fold increase 
in risk for developing IDDM.

Rheumatoid arthritis: if you express DR4, you have a 4.2 fold increase in 
risk.

multiple sclerosis: DR2 - 5 fold increase risk.

SLE: females 10-20 times more likely to get, same w/MS. estrogens 
upregulate gene which produces IFNg. this can explain why these dz are 
cyclical and why they occur more often in females.

if you have HLA B8, unlikely to get RA, but if DR4, much more likely. 
IDDM - risk increases w/coexpression of various gene families.

just know there is an association w/MHCII. it always turns out if you 
have DR3 and DR4 you are more likely to have IDDM than having one or the 
other or anything else.

remember MHCII has open ends and can hold large molecule. it's known that 
at the beta chain on the end, if there's an aspartic acid you are 
resistant to IDDM. further, in japanese people, most of them have that 
aspartic acid there, and only 5% of population in japan gets IDDM. in 
caucasians, most people have valine, serine, or alanine. so here, a 
single AA substitution in beta chain predisposes people to being able to 
present this self epitope to the immune system.

don't get impression that HLA is the only gene product or sole one 
determining risk for diabetes. some people have DR3 and DR4 and are fine, 
and some diabetics don't have DR3/DR4 and have diabetes. this is a 
predisposition, not a sole determining factor.

if you overexpress self epitopes with IFNg

diabetic human: has MHCII on insulin cells
normal human stimulated w/IFNg has no expression of MHCII on insulin 
cells.
normal human stimulated w/IFNg and TNF makes MHC on insulin cells, 
somatostatin cells, and glucagon cells. 

these cytokines can upregulate mhcII and then you can present 
self-epitopes to the immune system.

rats prone to diabetes: IFNg causes MHCII to show up on insulin cells
diabetes resistant rats: IFNg does NOT cause MHCII to show up on insulin 
cells.

think of the brain: it doesn't normally express MHC I or MHC II. but, 
when you have MS (demyelinating dz), IFNg can upregulate expression of 
MHCI and MHCII and you start presenting epitopes...

organ specific autoimmune dz in dog: PEMPHIGUS. at mucocutaneous junction 
of oral cavity - hairloss, erosion of superficial epi with hemorrhage and 
inflammatory response. also at nailbeds and at medial canthus. if you 
look at the involved tissues you find that you have an Ab being produced 
against desmosomal proteins that normally cause keratinocytes to adhere 
to eachother tightly. what happens is there are antibodies, not a lot of 
complement involvement...when Ab binds desmosomal proteins, it activates 
the keratinocytes, causing them to liberate a bunch of enzymes which 
break down proteins between the cells, triggering inflammatory response. 
T cells aren't really involved either. it's a rather unusual situation 
called Pemphigus Vulgaris.

there are different kinds of pemphigus lesions.

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common manifestations of SLE...
anti DNA Abs are the ones causing the immune complex deposition in blood 
vessels, glomeruli, and synovial membranes. anemia is caused by anti RBC 
Ab, not anti DNA Ab.

patients w/SLE in kidney will have weird distribution pattern in 
glomerulus ofimmune complexes. Anti BM ab causes linear distribution.

how to test for lupus? take tissue culture cells from any species, 
because thereis a lot of cross reactivity. you have to fix and 
permeablize the cells so Ab can penetrate, then you bathe cells w/control 
serum and patient serum, and add fluorescien conjugated Ab,and you will 
see glow. this is ANA antinuclear antibody test.

rheumatoid arthritis occurs rarely in dogs. see erosion and destruction 
of cartilage. synovial membrane is elevated, glistening, irregular 
-should be smooth. also red: inflammation.

what is the Ag in rheumatoid arthritis? it's complicated but not too 
difficult. the purported Ag that may trigger something in the joint could 
be virus, mycoplasma, klebsiella, something. a normal interaction between 
Ag and Ab would lead after it forms a complex to somehow a triggering of 
the exposure of the constant region of the Ig which the immune system 
recognizes as being different. why does't this occur all the time? well, 
it does. there is always exposure of part of Fc after Ag/Ab complex 
forms. but some people are predisposed to making an antibody to the Fc 
portion. they make a 'rheumatoid factor' which is an Ab against the Fc 
portion of your own anti-ag antibody (your own Ig). so you now have Ab 
against your own Ig, and you get complexes, which happen to be primarily 
in the joint nad which will now do a type III immune complex dz 
thing...fix complement, C3a C5a, destruction of tissue, via lysosomal 
enzymes. end result: you get this occuring chronically, repeated 
episodes, repeated acute inflammatrory responses causign desstruction of 
joint: ankylosis of joints, fibrosis, destruction of cartilage. 

can rheumatoid factor sneak out into circulation? yes. and that's how 
patients are tested - for presence of rf in circulation. but do you get 
immune complexesin the circulation? sure, you can, and hen you see 
glomerulonephritis and other problems. so if patient has a lot of 
rheumatoid factor in the blood, they could have destruction of glomeruli 
as well.

another dz where people know alot of stuff. MS multiple sclerosis.this is 
a demyelinating dz which attacks myelin basic sheath around axon which 
starts at neuron and goes to effector site. MS patients have attack in 
white matter in brain, primarily. cellular composition of lesion:

Th1 cells, mostly. releaseing TNF, lymphotoxin, IFNg, which activates 
macrophages and MHCI and II. so the IFNg really precipitates an 
inflammatory response.

B cells produce Ab to MBP. cause complement fixation. also destroy 
oligodendrocytes.

macrophages: release TNF, directly attack myelin sheath when activated. 
activated mphages in brain is very bad.

how is MS triggered?

adenovirus type II -- has AA sequence like that in crucial fragment of 
MBP. so assumption is that if you get adenovirus II, you start making Ab 
against that virus,but the Ab will cross react with your MBP.

hepatitis B virus polymerase--shares 6 AA fragment with part of MBP that 
causes EAE in rabbits. if you immunize with that viral portion you get 
EAE. you inject with an adjuvant to stimulate response.

participation of superantigens comes into play w/MS. superantigen binds 
to MHCII and to vbeta portion of TcR. animals usually have restricted 
number of vbeta forms of beta chain of TcR, and superantigen will bind to 
that and nonspecifically trigger a huge number of T cells.
if your patient has MS and T cells are involved, if these patients get 
exposed to staphylococcal enterotoxin B, a superantigen, they can get an 
exacerbation from that, due to nonspecific activation of T cells, som eof 
which are specific for MBP.

if you induce EAE in mouse, and let animal recover, and then give staph. 
enterotoxin B, they get relapse based on above mechanism. SEB increases 
broad t cell activity by binding to TcR outside the specific recognition 
site.

if you have an animal w/autoimmune dz eg dog, most economical way to 
treat animal is to give steroids. steroids are antiinflammatory drugs 
which will ameliorate a lot of the problems. also could give cyclosporin 
if mainly T cell mediated, though that costs more. organ specific dz, try 
to give the missing product eg thyroxine, insulin.

going back to MS..how do you try to deal with this dz? downregulate 
expression of HLA (MHCI, II) in the brain  with IFNb  - causes a 30% 
reduction in attacks, decreased areas of inflammation in the brain. 
approved tx method

make analogue of MBP to bind HLA with higher affinity than native MBP, 
which isn't immunogenic. this is experimental. want to make something 
like myelin, so the HLA groove can't present your own myelin.

make mononuclear Abs that bind to TNF - clears TNF from circulation, 
suppresses autoimmune response for 5-10 wks.

use monoclonal Abs to VLA4 or ICAM1 (adhesion molecules)- prevents T cell 
adhesion to vessels in areas of inflammation: prevents EAEin rats, 
deccreases rheumatoid arthritis. keeps WBCs from getting into brain by 
reducing presence of adhesion molecules.

feed MBP: triggers T cells to make TGFb which counters TNF and IFNg, 
prevents EAE in rodents. this is a tolerance mechanism. if you feed 
bovine MBP and induce oral tolerance, somehow triggering the TGFb immune 
downregulatory sequence, you can prevent exacerbations. people have been 
fed this stuff experimentally- more effective in men than in women. why? 
women mke more estrogens and more IFNg so harder to regulate. 

tx: IFNb, feeding boving MBP -these are used in people.

don't skip class monday.

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