( There ( ( are ( ( ( many ( other antigens ) ) ( -LRB- ( ( weaker ( that ( ( ABO and ) Rh ) ) ) -RRB- ) ) ) ( that ( usually ( ( do n't ) ( have ( to ( be ( matched ( because ( ( transfusion ( of ( blood ( ( containing ( one ( of ( these antigens ) ) ) ) ( to ( ( a patient ) ( ( lacking ( this antigen ) ) rarely ) ) ) ) ) ) ) ( causes ( production ( of ( antibodies ( -LRB- ( ( proteins ( that ( react ( with ( the antigens ) ) ) ) ) -RRB- ) ) ) ) ) ) ) ) ) ) ) ) ) ) ) ) ) . ) )
(ROOT (S (NP (EX There)) (VP (VBP are) (NP (NP (JJ many) (JJ other) (NNS antigens)) (PRN (-LRB- -LRB-) (ADJP (JJR weaker) (PP (IN that) (NP (NNP ABO) (CC and) (NNP Rh)))) (-RRB- -RRB-)) (SBAR (WHNP (WDT that)) (S (ADVP (RB usually)) (VP (VBP do) (RB n't) (VP (VB have) (S (VP (TO to) (VP (VB be) (VP (VBN matched) (SBAR (IN because) (S (NP (NP (NN transfusion)) (PP (IN of) (NP (NP (NN blood)) (VP (VBG containing) (NP (NP (CD one)) (PP (IN of) (NP (DT these) (NNS antigens)))) (PP (TO to) (NP (NP (DT a) (NN patient)) (VP (VBG lacking) (NP (DT this) (NN antigen)) (ADVP (RB rarely))))))))) (VP (VBZ causes) (NP (NP (NN production)) (PP (IN of) (NP (NP (NNS antibodies)) (PRN (-LRB- -LRB-) (NP (NP (NNS proteins)) (SBAR (WHNP (WDT that)) (S (VP (VBP react) (PP (IN with) (NP (DT the) (NNS antigens))))))) (-RRB- -RRB-)))))))))))))))))) (. .)))
There are many other antigens (weaker that ABO and Rh) that usually don't have to be matched because transfusion of blood containing one of these antigens to a patient lacking this antigen rarely causes production of antibodies (proteins that  react with the antigens).
(ROOT (S (NP (DT An) (NN antibody)) (VP (MD can) (VP (VB match) (NP (NP (CD one) (NNS types)) (PP (IN of) (NP (NNS antigens)))))) (. .)))